The free Keyboard Repair Program does not necessarily always have to replace a part. One of the first steps an Apple tech will do is attempt to clean the keyboard using compressed air since some key issues are due to dirt & crumbs interfering with the butterfly mechanism (it does not take much to gum of the butterfly mechanism).
How to clean the keyboard of your MacBook or MacBook Pro - Apple Support
Here are the public details regarding the free Apple Keyboard Repair program (make note of the section which mentions Apple may only replace a key if appropriate):
Keyboard Service Program for MacBook, MacBook Air, and MacBook Pro - Apple Support
Second an Apple tech will attempt to replace the key caps on the keys which are having issues.
If the key still does not work correctly, then and only then will Apple replace the Keyboard for free under the free Keyboard repair program as long as the laptop is less than four years old (read the fine print for some exceptions).
I can tell you from personal experience from supporting thousands of our organization's Macs, that many times the key issues are due to dirt & crumbs. I have actually developed some techniques for isolating a bad key which would qualify for the free repair program since I understand the basics of why the keys fail -- due to a combination of poor design for the key switch and possibly manufacturing issues as well. Basically the key switch is just a plastic bubble that closes a circuit, but this plastic bubble is not sturdy so it weakens quickly which results in either the circuit not being closed or by the key switch not popping back up to break the circuit quickly enough. In my own personal experience supporting thousands of our organization's Macs, it seems like certain keys are more likely to show this issue. Dirt & crumbs can also cause this problem by pressing on the plastic key switch bubble or by causing the butterfly mechanism to stick or jam.
I can certainly understand your frustration though as the Butterfly keyboard is an absolutely terrible design in my opinion feels terrible when typing.
Just be grateful that the tech is actually going to perform a battery replacement since the cost of Battery replacement is much less expensive than having to pay for a Keyboard repair, yet both repairs will result in exactly the same end result of a new Top Case Assembly which includes the Keyboard, Trackpad, Battery and for the Touchbar models it will also include the Touchbar and Speakers. I have seen some users report paying full price for the Top Case Assembly when both a keyboard and the battery issue exists. I have also seen some people report getting the Battery quote and refusing, only to go back later with another tech who quotes them the more expensive repair due to the key issue.
I hope this helps you to understand the complexity of the situation. It really does not help that Apple has combined what used to be smaller individual items into one major component. On much older laptops, the Top Case, keyboard, trackpad, battery, speakers were all individual parts that could be replaced independent of one another. But Apple has combined all these formerly individual parts into one single part partially to help make the laptops slimmer which also greatly increases the cost of repairs.
You can always leave Apple with product feedback (Apple won't respond):
Product Feedback - Apple