Testing the game on multiple configurations is part of the Quality Assurance (QA) process of every well-organized game project. 

Larger studios can afford to have whole QA labs stacked with dozens of PCs in all imaginable configurations, pay an army of QA testers to play the game on all of them and have them report performance or compatibility problems to the development team. When the developers can not reproduce the problems on their development machines, then they usually have to borrow one of those test machines to reproduce and fix the problem. 

Smaller development teams or solo developer of course don't have the resources to afford that. Nevertheless it can still be a good idea to have an older/weaker PC around to check from time to time if the game still runs on it. Even just having a single other PC available for testing can catch a lot of those "works on my machine" problems. 

But intentionally doing everything on a weak PC when a stronger one is available to you is just masochism. Developers run lots of tools in parallel to the game which require resources, and also do various amounts of offline processing which takes time. So using suboptimal hardware is just hampering your work experience.

Also keep in mind that technology marches on while you are developing your game. When your game is planned for release in 5 years, then the high-end gaming PC you are sitting on right now will be an outdated model on release day. So developing your game for your current specs will give you a pretty wide audience in 5 years. That means if you are going to treat yourself with a new Intel Core i11-14909 and an RTX 5090 in a couple years, don't eBay the old one right away.