Quite a few have had similar reactions to custards...
Many, many posts about this. Here's one-
Capella Vanilla Custard....Odd Feeling in Throat after Vaping | E-Cigarette Forum
Lol- You Quote a thread by a Noob DIY'er not having the proper equipment or knowledge to correctly mix and sample as Evidence of What exactly?
Follow up post were of little value.
Vanilla a NON-Diketone - can be Extremely Harsh on the Throat
PG for some is Extremely Harsh
Ethel Malto can be Harsh on the throat
Your Blurb post are not helpful to new members seeking advice or assistance.

I await information from the Op to attempt to assist.