Ask the same question to Apple support via online chat. Be very specific in your question. They will let you know there is no such 80% requirement.
Print out the chat log. Bring it to the Apple Store. Ask for the store manager if the front line staff refuses.
I’ve had a similar experience dealing with some iPhone battery replacements. Once you show them the chat log, they should back down.
I believe this is true for iphones since they can indeed replace the battery individually (although it's not an easy process so they'd prefer not to do it). But are you certain that this is true for macbook, since it requires a full-top case replacement? Unless you get a really friendly manager who's willing to override, the policy that I've always seen (and have been quoted 2 separate times) is that you don't get any soup if you're above 80%. One can argue with them about acceptable tolerance, reported BMS capacity changing with SoC, etc. but the so-called geniuses will only authorize a replacement if MRI shows it as below 80% (or maybe also consumed?).
The flipside is that you if are really borderline, like 81% or so, it might well be possible to spike the odds in your favor by attempting to get the BMS to recompute capacity since I have seen ±3% variation as SoC changes. You should try checking the capacity when holding at various levels of SoC, e.g. at 100%, 80%, 20%, and 10%. With any luck the resistance on one of them might be higher which could be enough to push you beyond 80% cutoff. Then you only need to go to the genius bar and ensure you are at that SoC when testing.
I tried this myself, and unfortunately for me capacity at lower SoC was actually slightly higher (84% @ 25% SoC, 85% at 10% SoC) so the overall range of capacity across SoC is (83%-85%). Another trick you can try is running a calibration cycle with heavy load (e.g. using external graphics card, playing game, connecting display, etc.) which should decrease the voltage seen by the BMS and possibly throw off its capacity estimation (I am not privy to the exact algorithms the BMS uses but it's probably some variant of coloumb counting combined with voltage tracking).
And I mentioned this before, but if you want to really go all out (and have a machine you don't mind potentially risking) you can flash the smc with a modified firmware that would allow you to change the reported capacity value. Would love to see someone actually do this (but time is running out... not sure if this can be done on T1+ machines and the last non-T1, 2015 mbp, will be marked vintage soon).
Doesn’t work if your device is about to be classified as obsolete….
Or if you are going to be traveling and won’t have access to an Apple Store for a while….
Sure if you can wait, then this discussion point isn’t really an issue for you…..
I'm surprised apple hasn't been sued yet for the glued battery. They do end up relenting when these movements get enough traction (2011 gpu, ios battery throttling), and so even if they cannot change the batteries themselves, they should at least make OEM batteries available for those willing to scrape off the glue. I believe that apple did recently announce a program for these parts, but I highly doubt they will include the vintage/obsolete models.
Interestingly their vintage/obsolete pages does state "Additionally, Mac notebooks **may be eligible for an extended battery-only repair period for up to 10 years from when the product was last distributed for sale**, subject to parts availability." Anyone want to go in with a 2012 rmbp and see what they do? With the amount of weasel words in there I highly doubt they will actually service anything that's marked as obsolete.