The max option was being applied too late:

When expanding a single large numeric range like {1..10000000}, the sequence generation loop generates all 10 million intermediate elements before the max limit is applied With max=10, the output is correctly limited to 10 items, but the process still allocates ~505 MB and spends ~800ms building the full intermediate array.

Workaround

Ensure the string to be expanded doesn't contain more values than the desired max item count.