@dunroving - you should be in the clear because it's backdated to December 2023 - so not 20 months, but 8 months and you'll have the refund impact to consider
I'm in the first category having being WEP'ed since Day 1 (November 2021). I'm not holding my breath on how fast the SSA will work their way through this as I imagine it will require quite a software update and then everything that goes along with that - it could be several months. The "minor refund" that you refer to is in my case (and by my own calculations), anything but minor - because of it being backdated to December 2023.
All cases and amounts will be different, but the maximum amount of WEP for an individual was $587 per month in 2024 (someone with less than 20 years contributions but with high ELY (Eligibility Year Benefits)). When this is coupled with a related spousal benefit - it can then be $881 per month. Multiply that by 12 months and some can be looking at a retro refund in excess of $10k - which will increase further if SSA get behind on implementing the changes.
Let's see how fast SSA work - I imagine they'll be under a lot of pressure because the vast majority of those impacted by WEP are in the US and are retired public servants.
Interestingly, I logged into the MySSA account earlier and it was showing (in the "Payment History" section, drop-down menu from January 2025 payment) zero deduction for overpayments (so, only a WEP reduction), same as my December 2024 payment (so, same WEP reduction but no clawback).
As you say, it will likely take a lot of work to programme refunds, but it should be fairly easy to cancel WEP reductions from early 2025.
Even more interesting (perhaps) is that I looked back at my confusing WEP letter of a couple of weeks back (I posted about this in the "Delays at the SSA?" thread, in case it's of interest). I reported that, in that letter, they said: "You have an overpayment of $1,542", which seemed rather low for 20 months of un-deducted WEP.
It then said, "You received $956 04-2023 to 11/2023. You should have received $697 04-2023 to 11/2023"
It's only just dawned on me that the letter is only referring to 2023 (not 2024, when I was also overpaid, with no WEP adjustment). I wonder whether this (not mentioning 2024) was in anticipation that the 2024 overpayments would become moot (even though the letter was sent before the WEP repeal was signed). It makes a lot more sense now ...