I would think that putting liquid salt in a a glass pipe is somewhat asking for trouble. One of the many issues with glass is "thermal shock".
Let's say there is a fire and water based sprinklers are activated.. what will the 1,400F glass do once water touches it?
Or there is an accident and someone bangs into the glass. Metal can deform and not fail, glass cant.
A molten salt reactor is a material science problem. Conventional “metal” doesn’t work because of the corrosion. If glass has some desirable property then we can overcome the “bumping in to it” problem. Maybe with a hand rail. Or staying away from the operational nuclear reactor.
I’m not suggesting glass actually be used. I’m saying if it was I wouldn’t be surprised.
What point are you trying to make here?
Salt melts at 1474 F.
Metals also have weird properties. Like tempering and hardening based on temperature. In an industrial setting you need expert welders with deep knowledge of the materials or a weld is going to fail and ruin your day.
So it doesn't seem like a huge leap to me actually, assuming ceramics or glass actually have desirable properties.