the server should be able to let a client start animations.
a example i have encountered when i was modding is that you cant say to the client eat. even though it would take the item away when you are at full hunger the eating animation did not start because the client and server where not synchronized.
Justification and Use Case:
i wanted to not automatically have health regeneration but make it also not that you can only regeneration heath with golden apples, instead i went with all food eaten regaining a bit of health, i wanted to be able to eat even when hunger is full, but health not. i can also see this working for other animations like fishing where the client says i wand to fish and the server then says do a swing.
there is the problem with lag on the server, a possibility is that the server sends when a animation should be occur when sending server info.
this may seem as a fix for not a big problem but it could help making modding go towards more server side instead of needing to mod both client and server.