What a great idea to childproof the instant hot.

I missed your original thread, but I have a similar drinking water setup as you without the tapmaster. There's something I've noticed that hasn't been mentioned, at least I don't remember seeing it. The instahot has to vent through drinking faucet. Occasionally the drinking faucet will hiss or gurgle a little as the instahot tank is releasing pressure. Will the Tapmaster installation you have prevent this kind of venting? If not, it might lessen the life of the system. I know I could probably turn mine down to never have any venting, but then it wouldn't be hot enough. Just something to consider in case it matters.

the open to air venting is still present no matter how many additional valves are placed in the pipe leading to the tank. Open to air venting means that the water in the pipe (or tube) between the tank and the faucet is not pressurized water. Regular faucets are the opposite: they have a valve at the end of the pipe, so pressurized water is in the pipe leading to the faucet.

Instant scalding hot tanks are always set up differently. Look at the PDFs and you will see lots of pipes or tubes going back and forth. An IHW faucet valve sends water into the IHW tank which then pushes boiling hot water out of the tank, by displacement. So, schematically, it's a valve in the pipe going to the tank, not a valve at the end of the line.

It's one of the reasons why these faucets are special and different.

Mine still hisses and gurgles, the tap master is actually installed on the inflow side, not the outflow side. Somehow it still works, but it does hiss and gurgle.

Ah, that makes sense. You shouldn't have any issues. Looks like a fine solution.