Demonstration of blocks in post content that cause fetchpriority to be omitted on the LCP image (and from all images)

wordpress-fetchpriority-absent-on-image.post_content.html

<!-- wp:columns {"isStackedOnMobile":false} -->
<div class="wp-block-columns is-not-stacked-on-mobile"><!-- wp:column {"layout":{"type":"default"}} -->
<div class="wp-block-column"><!-- wp:image {"align":"center","id":112,"sizeSlug":"thumbnail"} -->
<figure class="wp-block-image aligncenter size-thumbnail"><img src="http://localhost:8889/wp-content/uploads/2023/09/image-150x150.jpeg" alt="" class="wp-image-112"/></figure>
<!-- /wp:image --></div>
<!-- /wp:column -->

<!-- wp:column -->
<div class="wp-block-column"><!-- wp:image {"align":"center","id":113,"sizeSlug":"thumbnail"} -->
<figure class="wp-block-image aligncenter size-thumbnail"><img src="http://localhost:8889/wp-content/uploads/2023/09/image-1-150x150.jpeg" alt="" class="wp-image-113"/></figure>
<!-- /wp:image --></div>
<!-- /wp:column -->

<!-- wp:column -->
<div class="wp-block-column"><!-- wp:image {"align":"center","id":114,"sizeSlug":"thumbnail"} -->
<figure class="wp-block-image aligncenter size-thumbnail"><img src="http://localhost:8889/wp-content/uploads/2023/09/image-2-150x150.jpeg" alt="" class="wp-image-114"/></figure>
<!-- /wp:image --></div>
<!-- /wp:column --></div>
<!-- /wp:columns -->

<!-- wp:image {"id":115} -->
<figure class="wp-block-image"><img src="http://localhost:8889/wp-content/uploads/2023/09/image-3.jpeg" alt="" class="wp-image-115"/><figcaption class="wp-element-caption">"<a href="https://www.rawpixel.com/image/8718239/photo-image-moon-space-planet" target="_blank" rel="noreferrer noopener">Taken by Apollo 8 crewmember</a>"/ <a href="https://creativecommons.org/publicdomain/zero/1.0/?ref=openverse" target="_blank" rel="noreferrer noopener">CC0 1.0</a></figcaption></figure>
<!-- /wp:image -->

wordpress-fetchpriority-absent-on-image.rendered_blocks.html

<div
  class="wp-block-columns is-not-stacked-on-mobile is-layout-flex wp-container-9 wp-block-columns-is-layout-flex"
>
  <div class="wp-block-column is-layout-flow wp-block-column-is-layout-flow">
    <figure class="wp-block-image aligncenter size-thumbnail">
      <img
        decoding="async"
        width="150"
        height="150"
        src="http://localhost:8889/wp-content/uploads/2023/09/image-150x150.jpeg"
        alt=""
        class="wp-image-112"
      />
    </figure>
  </div>

  <div class="wp-block-column is-layout-flow wp-block-column-is-layout-flow">
    <figure class="wp-block-image aligncenter size-thumbnail">
      <img
        decoding="async"
        width="150"
        height="150"
        src="http://localhost:8889/wp-content/uploads/2023/09/image-1-150x150.jpeg"
        alt=""
        class="wp-image-113"
      />
    </figure>
  </div>

  <div class="wp-block-column is-layout-flow wp-block-column-is-layout-flow">
    <figure class="wp-block-image aligncenter size-thumbnail">
      <img
        decoding="async"
        width="150"
        height="150"
        src="http://localhost:8889/wp-content/uploads/2023/09/image-2-150x150.jpeg"
        alt=""
        class="wp-image-114"
        srcset="
          http://localhost:8889/wp-content/uploads/2023/09/image-2-150x150.jpeg  150w,
          http://localhost:8889/wp-content/uploads/2023/09/image-2-300x300.jpeg  300w,
          http://localhost:8889/wp-content/uploads/2023/09/image-2-768x768.jpeg  768w,
          http://localhost:8889/wp-content/uploads/2023/09/image-2.jpeg         1024w
        "
        sizes="(max-width: 150px) 100vw, 150px"
      />
    </figure>
  </div>
</div>

<figure class="wp-block-image">
  <img
    decoding="async"
    loading="lazy"
    width="1300"
    height="1300"
    src="http://localhost:8889/wp-content/uploads/2023/09/image-3.jpeg"
    alt=""
    class="wp-image-115"
    srcset="
      http://localhost:8889/wp-content/uploads/2023/09/image-3.jpeg           1300w,
      http://localhost:8889/wp-content/uploads/2023/09/image-3-300x300.jpeg    300w,
      http://localhost:8889/wp-content/uploads/2023/09/image-3-1024x1024.jpeg 1024w,
      http://localhost:8889/wp-content/uploads/2023/09/image-3-150x150.jpeg    150w,
      http://localhost:8889/wp-content/uploads/2023/09/image-3-768x768.jpeg    768w
    "
    sizes="(max-width: 1300px) 100vw, 1300px"
  />
  <figcaption class="wp-element-caption">
    &#8220;<a
      href="https://www.rawpixel.com/image/8718239/photo-image-moon-space-planet"
      target="_blank"
      rel="noreferrer noopener"
      >Taken by Apollo 8 crewmember</a
    >&#8220;/
    <a
      href="https://creativecommons.org/publicdomain/zero/1.0/?ref=openverse"
      target="_blank"
      rel="noreferrer noopener"
      >CC0 1.0</a
    >
  </figcaption>
</figure>

The 4th image is incorrectly getting loading=lazy and is omitting fetchpriority=high, even though it is the LCP image: