Answer
If you set Cross Platform Play to Disabled in Apex Legends, matchmaking is limited to players on the same platform who also have cross-play disabled.
That means queue times may be longer. If you want faster matchmaking, leaving cross-play enabled is usually the safer choice.
Caveats
According to EA official help, PC players cannot turn cross-play off. On console, treat Cross Platform Play set to Disabled as a tradeoff between same-platform matchmaking and queue time.