I just ran into this today. I had set a wonky layer name that was descriptive of the processing I applied to create the raster layer (a different spatial reference). I assumed I could change the name in the web map. Nope. I also ended up needing to recreate the tpkx, upload and create a NEW tile layer. When I tried to replace it with the new, it said something didn't match. Other then the name, all the tiling and such was the same. But it also appears some enhancements were made to the way tiles are stored. It is less than 1/4 the size of the original (created in Sept. 2025). And creating the new tile package, uploading, and publishing the tile layer was also much faster.
This entire workflow could be improved. There are too many opportunities for varying settings and options creeping in that have no effective impact on the result, but apparently cause the new tpkx to not "match" the old. One should be able to point to a tile layer in ArcGIS Online, or at least the tpkx, and have the geoprocessing tool options be filled in automatically to match the old. If something fails there at least you'd know it before generating a new tpkx that isn't going to work after uploading. And this workflow could have an option for automatically updating the tile layer from the uploaded tpkx rather than needing another manual step.
