False. Usually it’s just as easy if not easier to configure your dev server to listen on 0.0.0.0 instead of 127.0.0.1, and these days most sites are mobile first, so it’s very natural to develop on your computer and test on a phone in the same LAN. Figuring out accessing your computer via 192.168.0.x is way easier than figuring out how to issue a LE cert (the easy part) and use it on your dev server (the hard part).
Before you mention mobile device simulation in desktop browsers, I’ll point out that mobile browsers often have quirks that are not present in desktop browser simulations. For instance, mobile Safari is subtly different from desktop Safari responsive design mode in many ways, and the only way that I know to actually simulate mobile Safari is with full-blown Simulator.app.