SBT build with optional dependency between subprojects, for IntelliJ bug report

build.sbt

ThisBuild / scalaVersion := "2.13.12"
ThisBuild / version := "1.0"
ThisBuild / organization := "com.example"

lazy val root = (project in file("."))
	.aggregate(libA, libB)

lazy val libA = (project in file("libA"))
	.settings(name := "libA")

lazy val libB = (project in file("libB"))
	.dependsOn(libA % Optional)
	.settings(name := "libB")

UtilityA.scala

package com.example.liba

class UtilityA {

}

UtilityB.scala

package com.example.libb

import com.example.liba.UtilityA

object UtilityB {
	def normalMethod = println("normal")
	def helperMethod(utilA: UtilityA) = println(s"utility: $utilA")
}