well the manga suggests so, maybe bacause of the poison too.
Just to let you know, pre TS zoro already had durability and endurance feats. Pre TS zoro was able to fast for 9 days when he got caught by Helmeppo
Also, when he got stabbed by buggy, he proceeded to take up luffy along with the iron bar which could supposedly squits his guts, he then walked with it which made him lose even more bloods, after that the house in which he took a rest got boomed by a buggy ball. With him still suffering from injuries he fought Cabaji and got kicked two times right in the wound he had, and even got one more stab wound.
Moreover, he got severely wounded by Mihawk, he then fought Haachi and fought Arlong
We know current zoro is by far stronger than Pre TS zoro, if pre TS zoro could perform such great feats, i expected more from zoro, but then he fainted from only one Killer's attack. I dont know if that is PIS or not, take it as you will