I do not work for Apple.
I do not speak for Apple.
[in my opinion] Strictly as fellow Mac User, armed with the information that the complex battery-trackpad-keyboard-topPlate module is the one that would be replaced in either situation, I would cancel that repair order and submit my MacBook Pro for a battery replacement.
The standard charge is US$250. Then adding on shipping, that looks like an under US$300 repair instead of a under US$800 repair.
PROVIDED that you have NO OTHER unresolved issues not disclosed here, that is likely to get you the needed relief at a lower overall cost.
NB>> if you have other festering issues not mentioned here, you will be facing an ADDITIONAL repair at the US$800 level later.
¿have you run the user diagnostic to check for other GROSS issues?
(it does not generally find nuanced problems.)