Earlier quoted context omitted.
You should be able to do 50% of mediums Great. So if they give you 2 or 3 mediums in the course of the interview process, with a strict 30 minute deadline -- what is your chance of failing?
they usually do 2 medium problems in 45-50 minutes, first one is generally an easy medium, second is a bit more challenging. Chance of failing is dependent on many variables, you should practice some leetcode and hope that luck is on your side.
If they were as smart as they think they are - you'd think they'd come up with a system that wasn't so luck-dependent.