Replacement of Battery MacBook Pro (Retina, 13-inch, Early 2015)
Does Battery replacement (MacBook Pro (Retina, 13-inch, Early 2015) means that entire key board will also be replace or only the battery
MacBook Pro 13″, macOS 10.15
The whole Top Case/Keyboard Assembly will be replaced including the Trackpad especially if the repair is performed at the service location. If the Apple Store or service provider sends the laptop to an Apple mail-in repair depot, then I'm not certain, but I think the whole Top Case Assembly will still be replaced. I do know that Apple has on occasion been known to replace just the battery such as for the Battery Recall Program for the 15" model due to the number of repairs they expected to receive in a short time period (this helped to prevent a part shortage for people needing a keyboard or trackpad repair).
I still highly recommend the official Apple battery repair regardless because I've found the quality of third party Lithium-ion Batteries to be extremely poor and usually the official Apple batteries are much better quality. I will only grudgingly use a third party Lithium-ion battery only when an official Apple battery is not available.