Right you are! Because we all know that Cosmic Boy, Saturn Girl and Lightning Lad lacked that ability.
(Very funny, my friend.)
Come on! Even the Subs had standards.
Then again:
Ambush Bug: What’s your power?
Infectious Lass: I… uh… I make people sick.
Ambush Bug: I’m sure you do. But seriously… (then uses his teleportation to clobber whomever the Lass was trying to divert his attention from.)
I left off that for most of the Silver Age, “the boot” would probably mean transfer to the Legion Reserve. Some time between when Sun Boy lost his powers the only time, and Bouncing Boy lost his the first time, it was decided that it was to extreme for someone to loses everything Legion upon the first meeting after powers were lost.
So now, let’s consider a scenario wherein members get the boot if a sufficiently worthy applicant can duplicate their power.
Consider Wildfire, who was named Erg-1 in his origin story.
Mon-El is in charge. Erg-1 firmly asserts that he wants to be a Legionnaire despite the daily danger of death. He is voted in after a meeting-wide display of his currently known powers.
Mon-El then reviews the powers.
He gently moves to send Phantom Girl to the Reserve.
Then Colossal Boy and Shrinking Violet.
Then Chemical King. (The writer had gotten his power wrong. Some fans have made a comparison to Metamorpho. Let’s ignore that for my scenario.)
Then Mon-El cautions the remaining single-powered Legionnaires that Erg-1 is still exploring what he can do, and more of the team may need to get the boot.
Not a very pleasant prospect. 
Phantom Girl: “I can also enter the Phantom Zone!..and TAKE PEOPLE WITH ME…ahem. Mon-El.”
“Pleased to meet you! What can you do without artificial devices or equipment?”
Excellent point, actually. We found out later that blowing out all his anti-energy didn’t kill him, as everyone thought, and as he himself expected or at least feared.
Without being at all snarky, we found out later that he was able to transport his “naked” self through interstellar space and then defeat a new villain, an android who was posing as an applicant.
But of course none of this was known to the Legion, so you are quite correct. In fact, when he compared his sight and vision favorably to Superboy’s, he said “though artificial” about them. It’s possible his flight power was also dependent on his containment suit. Or at least control over it, which of course is mandatory. Even his ability to mimic Salu, Gim, Condo Arlik, et al, depended on his containment suit in the sense that he (apparently) would not be able to survive at all without it.
That reminds me of a recurrent thought about certain story arcs. Did the writer intend to bring Drake back after a while from the start?
Or was he truly meant to be a One Shot Hero?
I would like to know once and for all, although he has not demonstrated the ability,does Ultra Boy have super hearing? Is it that he does possess it,maybe used it in secret ,but does not really focus on it. Same for Super Ventriliquism?