Here's a real experience from the Glasgow, UK Apple Store - it seems the memo about prioritising keyboard issues for next day replacement hasn't reached them.
This is with a 2018 MacBook Pro. It has had intermittent issues mostly with the space key producing two spaces for each press, but also a few issues like the 'o' key not responding properly sometimes. The issues started when the MacBook was less than 6 months old.
23rd May - Genius Bar appointment (it took me forever to actually find an appointment, there's been hardly any availability for a long time). Agreed to do a repair, but they don't have the keyboard in stock, will contact me.
5th June - keyboard arrives in stock! However I'm go abroad on 11th for 2 weeks, and they say they can't do the repair before I go even if I get the laptop to them straight away. So agree to take it in when I come back.
24th June - return from holiday but part has been released and used in someone else's repair so it needs to be ordered again
8th July - get in to see the Genius Bar and they still don't have the keyboard in stock so order one
12th July - part arrives again; drop laptop off; told they're going to attempt to clean/replace the mechanism first, which will take at least 72 hours, if that fails then they'll replace the whole keyboard which will take 5-7 days /on top of/ the 72 hours.
15th July - told Apple have cleaned & replaced the mechanism on the two switches
16th July - told laptop is ready for pickup & pick up laptop.
So I'm now waiting to see if the issue is resolved or not, but as the problem has been intermittent it's going to be a few days at least before I know, and if it hasn't I will have to go through the whole 'order part' dance again.
Overall I'm going to be most unhappy if the issue hasn't been resolved this time; I'm at the point where I'm likely to return the laptop rather than go through this process again, I've been using a borrowed 2013 MacBook whilst this one was in for repair and it's such a joy using a laptop where I don't have to spend half my time going back and removing extra spaces / full stops that randomly get added.