[Notably, Byleth didn't take a sip.]

I only 'won' the sparring matches where Jeralt was confirming my knowledge on certain techniques and arts.

[No point teaching someone a move and then just absolutely destroying them at the sparring match afterwards. No, to date, in a serious sparring match, Byleth has never won against Jeralt. His father was too wily, too experienced, and also wasn't afraid to cheat to win. 'Survival is all that matters', that's what he told him, and he ensured that lesson was beaten into Byleth's very bone marrow.]

Was your father equally formidable, Claude?