Item entities with a max_stack_size greater than 64 won't form stacks greater than 64

The bug

Item entities merge into larger stacks when nearby, to a maximum of 64. However, this maximum applies even to items that have a max_stack_size larger than 64.

How to reproduce

1. /give @p snowball[max_stack_size=99] 99

2. Drop 63 of the snowballs on the ground

3. Drop one more (✔ it merges)

4. Drop another one (❌ it doesn’t)

Expected result

The items should continue merging to the max stack size of 99

Observed result

The items won’t merge to form a stack larger than 64