Perhaps you have answered your own question. 
In reality, money is only one part of equation (although for some people it has to be the only part of the equation, I understand that). (I knew at the time I backed the Librem 5 that it was not and is not the cheapest phone that I could buy. It depends therefore on what price I put on other less tangible benefits, and even on what price I put on my data, my privacy.)
Sure, I understand your point that a Librem 5 may not be the best way to learn Linux (for monetary reasons and for other reasons). But hey …
“Why not do both?”
Buy a cheapy second hand desktop computer to install Linux on for crash-test-dummy purposes and to learn on … while waiting for the Librem 5 to be delivered.