arai's theory.
Hm, a lot of strange interpretations are going on, but this is the way how I personally see it. For common ability stats, E = expert, D = ace, C = superhuman, B through A = beyond what a human being can accomplish/going to need some god/demonic/dragon/shinpi blood to get these kinds of stats. There are some other theories for this about how back then, in order to even survive people had to be stronger/tougher/faster. Well Bedivere did manage to run way faster than a normal modern human being could so it is possible.Hmm...? If that was the case then Saber wouldn't have been able to do the Return of the King of Knights thing (she returns to her life abilities momentarily. The Grail wouldn't have been able to do this if it hadn't gotten these abilities. Well, this could be chalked up to 'lolSaber is alive'). It's just how good/bad the Master is in what decides the Servants abilities. Like say, if Merlin was resurrected in the 4th Grail War (not summoned. Resurrected. Summoned would result in something like Kojiro) for some reason then spent 10 years or so screwing around and comes back and then summons a Servant. They might have even better abilities then they were in life because Merlin is such a great Master. Meanwhile, a modern magus could only get something like Rin!Saber. Berserker (or rather Illya) should be a bit better then average (as in if an average Master would have summoned him) I think. Unless someone can correct me.Tbh, I think what they mean by hs is actually servant.
Like 'when the hs is transferred from throne to servant, they usually get weakened'