I used to do chamber coatings exactly like that but my carpal tunnel finally said, "Nope!" I've also been chided by other carvers for using water glass.
Coating the chamber of a new, unsmoked pipe is a separate subject from rescuing an already-charred one.
As for waterglass... as with most things, the devil is in the details. How it is applied can result in everything from a virtual glass bowl insert to occupying/filling only the damaged portions of wood.
I'm aware that the online pipe world loves few things more than arguing about waterglass. That's because arguing about shit in general is how humans tend to behave when shielded by anonymity, and waterglass just happened to be handy 20 years ago. Now, there are arguments
about previous arguments concerning it. (I kid you not)
Me? Objective reality is all I pay attention to, and the
subjective reality (emotion based) occupants of Planet Earth have my full blessing to claw each other's eyes out while riding around in their clown car. And OBJECTIVELY, a chamber wall with a spiderweb of cured waterglass inhabiting the fissures of a previous burn behaves/smokes no differently than one which has no such repair.