It is still your alternate if it is designated as your alternate on your flight plan. If your fuel planning is predicated on destination, MA, alternate, then the airport is still your alternate.Once you start diverting (not change of destination) is it still your alternate? No. We have alt mins to give us a better chance of the alternate maintaining landing mins at the time we divert there.
If you recalculate to show burn from PPOS to the airport you had listed as your alternate, you have now performed a change of destination.
I understand this is contrary to what a lot of us have learned and I struggled greatly with it, but I can find support for it in the regs. What I cannot find support for in the regs (or any supporting documentation) is that your alternate is no longer an alternate once you are proceeding there. If you have a reg, legal interp, or anything that supports that claim, please share it.