Once you join a tournament you play at that tier level until the end of the tournament.
So even if you make the next tier if you retry the tournament it will be at the old tier.
If you buy clubs that are beyond that tier (trying to use master only equipment in a pro tourney) you will get an error and be unable to play until you replace the new equipment.
At the end of the day it is fair and only happens for a short time.
Hope this helps