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That's pretty scary actually. Not to tell you your business (but I will anyway since you're posting on the open internet as opposed to speaking directly to other colleagues), but imo a good instructor would have a conversation about the negatives of deep air and the merits of trimix or even recreational trimix/helitrox to help them make a better informed decision. Which in most cases leads to them realizing some form of trimix is a better option. The good instructors I'm friends with consider deep air old school and potentially dangerous for all involved. I would suspect of the 6 or 7 instructors I'm thinking of, maybe 1 would even consider teaching it and that's only with a very very long conversation on the negatives and risks of deep air.
You're welcome to dive with helium at 110', and that's fine. To say/imply it's not safe, however, ignores years of evidence to the contrary and is, imo, irresponsible as a professional. There are dive profiles, that due to the expected activity level, risk due to environment, etc. for which diving helium at such depths is prudent, but there are a lot more dives done in the 100-130' range that don't meet any of those criteria done every year than those where helium is worth the cost for most divers to reduce the negligible risk decrease helium would provide for most of those dives.
