I think he was just referring to the more "complex" body movement. There's no ruleset where that move would be illegal.

One guy is bad statistics ;)

There are tons of skinny freestyle wrestlers, especially lighter weight categories. Takuto Otoguro (reigning 65kg world champion) is very skinny. Yianni Diakomihalis (also 65kg) is skinny. Frank Chamizo, 2x world champion at 70kg and 65kg, is not skinny, but his arms are (all his weight is in his legs). Zaurbek Sidakov, reigning 70kg world champion, is quite skinny with long, lanky arms. Perhaps Priit was talking about Greco Roman? Or maybe he was talking about the heavy weights? Those guys do tend to be really jacked in the upper body. It's a common misunderstanding that height in of itself is a disadvantage in freestyle wrestling and judo. Actually it confers some advantage in freestyle wrestling in the tie-ups and also gives more reach. Height confers a very significant advantage in judo during grip fighting and posture breaking (good for osoto-gari, some variations of uchi-mata, some variations of ouchi-gari, basically any throw that relies on pushing down on the head, shoulders, or back). Oftentimes, those advantages are completely nullified by the fact that most skinny people are relatively weaker, and also have higher centers of gravity. So a lot of the most successful athletes do tend to be on the shorter, stockier side in grappling sports. But if it's a tall person who doesn't have a strength disadvantage (like Otoguro or Saitiev in freestyle wrestling, or countless tall judo-ka), then the advantage of height probably outweighs the higher center of gravity. Once again, the advantage is bigger in judo, hence why it's fairly common to see world champions who are significantly taller than the rest of their weight division and blessed with unusual strength (Daria Bilodid, Shinichi Shinohara, Teddy Riner, Avtandil Tchrikishvili, etc).