> Perhaps you don’t know that on a CRT the number of lines that can be displayed is variable. Any CRT can display 400 lines or 399 lines or 1000 lines or however many lines you need or want.

This isn't true. Besides there being only a finite number of distinct phosphors / grid holes, the electronics and logic driving the display can also only handle a limited range of frequencies.

As LCD pixel densities increase the situation becomes effectively the same.

Yea, I was deliberately simplifying so that I didn’t have to spend pages and pages on the subject. Suffice it to say that the display on your desk could handle quite a large range of display resolutions with equal ease. The portable TV you took to the beach or whatever might not be so flexible.