Yes they have truly messed it up! (good old blizz devs)…
From what I can see they have changed MH slot to from 16 to 15 , OH slot from 17 to 16…which means Back slot has changed from 15 (now MH) to 14…Which will affect Trinket 2 which was 14… Slot 14 is now 13 , Slot 12 is now 11…Slot 11 is now 10…It then seems that any slot below 10 can no longer use the /equipslot command at all???
Also I noted that if you macro /use X …to use an “on use” item…the slot numbering hasn’t changed …i.e. /equipslot 15 EQUIPS Main Hand …/use 15 …would USE your Back item!
Truly a complete mess! well done Blizz !
I also note that the Patch Notes on the Battlenet client haven’t been updated since Aug 2023! Great change control Blizz!