Been doing some testing for the past couple of days. XS Max PB5 and AW4 5.3.
If I wear my watch and keep it close, like 10-15 feet or less, my AW4 battery appears to last as it used to. At the end of that day my watch was at 63%. Means that 2 day use is back.
However ...
Today I have been doing the normal and my watch my be in another room, on my desk; in other words I am not making an attempt to keep my iPhone close to my watch. Both are wifi connected. It is now going on 8 hours and my AW4 is down to 41%. By this evening it will be close to dead.
Not sure the "what" yet. But it appears I have found something.