Apple watch series 8 lasts only 5 hours

Here is a "brief" description of my issue.

I bought a series 8 45mil apple watch in May of this year.  it stopped working properly on August 21st. The battery life went from lasting 18+ hours to under 6 overnight.

The battery life setting states it is 100% healthy

I troubleshooted it per apple's direction to no effect, reset to factory settings, both the phone and watch, unpair and repair etc..

I brought it into the Apple Store for support on 9/9.  They, Apple genius bar, documented that it was not working properly and did the same troubleshooting in store and sent me home to see if it worked.  Begrudgingly I did,  It did not work.

I brought it back later the same day and Apple sent it to their repair depot.  It returned 9/15 with them unable to diagnose the cause of the issue and recommend the same troubleshooting steps.

Those steps were done in store, again, and I was sent home to test.  They did not work. I returned to the store and Apple documented it again and sent it out again.

On 9/23 I got it back from them with the same notes and steps to troubleshoot.... again...  They did not work.

I called Apple support number and was connected to a "senior technician" that installed a "diagnostic package" onto my phone and watch and is now asking me to document and journal on my watch usage and email it to them to help them determine the issue.

I told them this is ridiculous.  Am I getting compensated for my time running these diagnostics?  They said " uh no."

I then just outright asked for my watch to be replaced.  The associate said they can't replace it until they can determine the cause of the issue is not software related.

I said if it's software related then a reset to factory defaults would have solved the issue.

They then stated it could be my phone's hardware that was the issue.

I then paired the watch to my wife's phone, same issue.

I escalated to the "Highest Technician" and they stated without the diagnostics logs being made their engineers could not solve the software issue for me.

I said this is obviously a hardware issue, their diagnostics are not catching and it's not my responsibility to R&D apples code for them.

Now I am here with an apple watch under both their normal warranty and their apple care + warranty that they are refusing to fix unless I do a diagnostic for them.

Is there any way to prove this is a hardware issue and/or fix a this "Software bug"