As is shown in the pictures below. Perhaps Mojang considers this release as 1.13-pre11😛.
MC-134129
Wrong warning message in 1.13 release before opening a world
Resolved
Duplicate
0
Fu Chunhao
(Unassigned)
Unconfirmed
Minecraft 1.13
Retrieved
It was my fault that I didn't search very carefully and try every possible key word before creating this issue... Please mark this as duplicated.