Hello,
Test:
Full inventory of dirt blocks, or any item that stacks
Drop 1 stack of the same block on ground
Have a partial stack of the item, every other slot is full
When picking up the full stack, the extra items are deleted.
Linked issues
Comments

Thank you for your report!
We're tracking this issue in MC-8409, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
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Duplicates MC-8409