You've probably seen the disdain that the resident troll shows for any technique that differs from his own biases and what he calls 'trad' so it is quite a revelation that the grand high priest of 'trad' woodworking hasn't heard of match planing.
It basically a way of planing the edges of two boards to ensure they match perfectly when you glue them together, possibly with a rub joint.
A quick google will give a number of links and videos, this one
https://confusedwoodworker.wordpress.com/tag/match-planing/ comes out near the top. It doesn't really explain the process but there are other.
Interestingly this
https://www.ukworkshop.co.uk/threads/match-planeing.21283/ is also near the top and is a short discussion from the early days (probably pre-Grim as he didn't weigh in on it). An interesting point is made by Paul Sellers about the plane sole that I hadn't considered before.
HTH