Actually you failed to note that the word "blade" is actually present in that sentence and the word "Sith Troopers" is absent in that sentence.
Let me explain something to you:
Fell (In this manner of use): To have succumbed, generally to an attack.
Beneath (In this manner of use): Underneath.
Blade: A cutting or thrusting weapon that has a long metal blade (Though obviously the lightsaber isn't a metal blade).
"Many Jedi fell beneath his blade". You provided the quote, and that's what it said. Now you have to prove that the fell beneath his blade in combat, that they fell beneath his blade in one-on-one combat, and that they were remotely impressive duelists in the first place. The profile doesn't say it wasn't in combat, but it doesn't say it was in combat. The profile doesn't say he had help, but it doesn't say he did it on his own. The profile doesn't say they weren't good duelists, but it doesn't say they were good duelists either. You're the one who has to prove that they were good duelists, seeing as you're the one bringing the point forward and presenting the evidence (In other words, you have the burden of proof). And unfortunately for you, "Many Jedi fell beneath his blade" doesn't cover that. Falling beneath his blade simply means that he's the one who dealt the final killing blow with his blade. It doesn't say anything about how it was performed.
It also fails to specify exactly what qualifies as "many". It could be anywhere from ten to ten thousand.
For your point of "It didn't say Sith Troopers" to work, it would have to have said that he did it on his own, with no help whatsoever. Because if it didn't, I have an equally valid and very similar defense of "It didn't say that he didn't have help with him either, only that he finished them". And considering he generally has help when you face him, it's not helping your argument much.