Hi Paul,
Correct. Is a short form. This was actually for 2023 plan year. Filing was completed on extension Answers to your bullet points below.
Was not the final return, and was not elected on the 5500. Still haven't seen 2024, and am under impression there are still assets in the plan.
No entry in Part III 8j, thus no reason to have entry in 13c(1)
Correct that transfers are really rollovers. Which once again points to no reason to add company A
While I'd expect this to not a big deal on the error, I'd like to see zero inference that company A had involvement with the company b plan or that any piece of the plan merged in. I'm guessing by default company A, (by way of purchasing company b) has some administrative tasks to do to completely close the books on plan b.