Latest Activities BP Block filter: use this filter to disable the Post activity about the Post being displayed.

bp-custom.php

<?php

/**
 * Use this filter to disable the Post activity about the Post being displayed.
 */
function test_bp_activity_block_latest_updates_args( $widget_args, $block_args ) {
	$actions = explode( ',', $widget_args['action'] );

	if ( isset( $block_args['postId'] ) && $block_args['postId'] && in_array( 'new_blog_post', $actions, true ) ) {
		$widget_args['scope']        = false;
		$widget_args['filter_query'] = array(
			'relation' => 'AND',
			array(
				'column'  => 'secondary_item_id',
				'value'   => (int) $block_args['postId'],
				'compare' => '!=',
			)
		);
	}

	return $widget_args;
}
add_filter( 'bp_activity_block_latest_updates_args', 'test_bp_activity_block_latest_updates_args', 10, 2 );