hello and welcome to the fourm,
that is an interesting idea. but alas rclone does not do that yet.
so, as a kinda, sorta, concept idea, can do the following. i am not saying this is practical but think it would work.
to force rclone to update the cache for the rclone mount
rclone copy file.txt pcloud:rclone rc vfs/refresh dir=pcloud: