The fix mentioned in the changelogs is about the incorrect rotation of the vanilla panorama (which is reported in MCPE-229841), so the fix mentioned in the changelog is correct and present in-game, they just incorrectly linked to the wrong bug report.
Although I still prefer if Mojang reconsider this and reopen this issue (or the parent issue that this bug report duplicates), as having different panorama rotations while using a resource packs that has custom panorama is just weird.
The fix mentioned in the changelogs is about the incorrect rotation of the vanilla panorama (which is reported in MCPE-229841), so the fix mentioned in the changelog is correct and present in-game, they just incorrectly linked to the wrong bug report.
Although I still prefer if Mojang reconsider this and reopen this issue (or the parent issue that this bug report duplicates), as having different panorama rotations while using a resource packs that has custom panorama is just weird.
Fixed in 26.0.27 Preview.
From my testing, no, the fix for this issue doesn’t fix MCPE-172710, both attack and breathing animations is still different.
That was entirely different issue, that one is about player position on mount while jumping, while this one about mount jump sounds being missing.