It enters your body and is absorbed by your bloodstream. Is the delivery mechanism the issue?

The delivery mechanism is certainly an issue here. Food additives are tested for how safe they are to ingest, and they are not tested for how safe they are to inhale. In general we know that there are a lot of compounds safe to ingest which are not safe to inhale.

Just to pick an obviously stupid example, I could chug a can of soda (or seltzer, if you prefer) in one go. It would contain around 2.2g of CO2. If you put that 2.2g of CO2 in my lungs, I would be dead. (Well, you would have to keep it there. It would at least be very painful.)

Or to pick another obviously stupid example, I could drink enough alcohol to kill myself. In most situations, I would vomit or pass out before I got to the fatal dose. But instead, I could give myself an alcohol enema and just die (which does happen, from time to time). So, delivery matters absolutely.

For the non-obvious examples we (at least) need data. If you are putting “high” concentrations of a chemical (for some appropriate definition of “high”) in your lungs you will want some good safety data. For ingestion we already have an FDA approval process. You may disagree with the methodology, but at least it’s there.

Digested material generally gets partially broken down by either the gastric mechanisms or the liver and other organs involved.

Hence dosage for injections/sublingual delivery is much lower than dosage for normal pills to swallow.

It's pretty rare, but yes, some people vape alcohol.

The idea behind banning the flavoring is to make is less appealing to children. I don't see why the way it's consumed matters.