There are a few things that raise the question in my mind - 1) if the participant terminated during the year but didn't take a distribution, his entire account balance, vested and unvested, would be attributed to him and included as part of his balance. It makes me wonder if the intention of the add-back is to put those participants that actually took distributions in the year they terminated in the same position as those that didn't. Both would fall off in subsequent years, so they're getting the same treatment in that regard; 2) I could interpret "distribution" in this context as meaning amounts distributed from the participant account, whether actually paid to the participant (or rolled over) or forfeited, especially considering...3) the use of the term "account balance" as opposed to "vested account balance" in the EOB, as I pointed out in my original post.
It makes sense to me what you're saying about the forfeitures staying in the plan, Mike - I guess what I'm postulating is that the forfeiture would be attribute to the specific participant that took the distribution for that one particular year, being the year of termination, in light of the treatment of participants who terminated during the but didn't take a distribution. In subsequent years, the forfeiture would either be out of the plan if used to pay expenses or captured in other participant's accounts via reallocation of the forfeiture.