@pk good analysis. Under the facts as given (not completely clearly) I think it is at least possible that house #2 was spouse A's main home for 2 years while spouse B remained living in house #1. Under that circumstance, the following is possible without implicating any false statements (maybe) being made.
@manchotroyal
Re-reading your original question:
If spouse A lived in the second home for more than 2 years, and owned the home at least 2 years, then spouse A is allowed to use their personal exclusion of $250,000 when selling the home (but not the $500,000 exclusion that would apply to both spouses, because both spouses did not use the home as their main home.)
In that case, then when you go to sell the first home this year, spouse B may claim a full $250,000 exclusion without amending the 2021 return, because spouse B did not use their exclusion in 2022.
However, in order to claim the full $500,000 exclusion in 2023 for spouses A and B, spouse A must file an amended 2022 return to remove the previous exclusion and pay the tax. Also, spouse A can only use their exclusion on the original home (selling in 2023) if they lived in the original home as their main home at least 731 days of the 5 years prior to the selling date, after deducting the time that spouse A lived in the second home as their main home.
In other words, each spouse considers their $250,000 exclusion separately. If we are correct that spouse A lived in the second home while spouse B remained in the first home, then if they sell home #1 today, spouse A can claim a 9/24ths exclusion ($93,750) using the hardship rule, while spouse B can claim a 100% exclusion ($250,000) using the 2 year/5 year rule, without having to amend 2022. If the gain is more than $343,750, then spouse A would have to file an amended 2022 return to remove the exclusion (or pay the tax, depending on how much gain their was in 2022 on house #2 compared to the gain today on house #1.)
