Yes they do have to do compromises, they do them all the time. Compromises on who to cater to and who to piss off, what to do if they don’t have senate, house, presidency… You don’t get to decide those compromises. They might not even know they’ll have to make them or it would just look bad so they don’t mention them.
Btw you can have a party holding +50% of the seats in multi-party democracy too. Could have “best of both”, if you are worried about parties having to fit into a coalition.