DB Plan - 415 Issue

I have a prior client who terminated their DB plan back in 2021. He recently applied for his benefit in the PWGA plan (he is deemed "a loan out corporation") and was expecting around 5,000/month. When we terminated his plan, he had 6 years of participation and received a lump sum based on 60% of the 2021 dollar limit. Logically, I feel he should still have 40% of the dollar limit left (he has over 10 years of participation when combined), but the PWGA plan froze the 415 dollar limit at the 2007 level. Because of this, they have taken the position that the 180,000 (prior to reductions) is the 415 limit and reduced his benefit to roughly 1,500 (claiming the full amount would violate 415). This is true if using the 180,000 dollar limit from 2007, but not an issue when using current dollar limits (following a good faith interpretation of 415 rules with MASD's)

For 415 aggregation purposes, it seems logical to use the unfrozen limit (allowing him to receive his full benefit in the PWGA plan), but I can't seem to find any guidance. Had he commenced benefits in the PWGA plan first, I would have reflected that benefit with the single employer plan and concluded there was no issue. Why should the order matter? Has anyone come across this issue?

Any help would be greatly appreciated!