I've not heard that dumb advice in years. Looking around real quick, I do still see a few how-to articles online and on Youtube.
We had a laptop about 11 years ago, where the nVidia card was defective. That model had widespread issues. We actually bought two identical laptops, the same day, at the same Microcenter. Mine still works 12 years later, and is still part of my portable studio/capture setup. Hers had issues right away, still covered by warranty.
The HP tech said he had to "re-float" the graphics card. "Reflow" is the term.
They essentially did the same thing as the lazy oven method, but with more precision: heat up the bad solder points. Another lazy/imprecise method is a heat gun, or even a hair dryer, both of which are safer than sticking electronics in an oven.
However, it's always temporary, if it even works at all. It's 50/50.
The card is defective. The solder points are bad.
HP had to "refloat" it 2-3 times. I eventually just gave her my "old" (but still newer) laptop, using AMD/ATI. Problem solved.
Point is, a new one = the real fix.
Over, heat gun, etc = temporary at best.
And since a graphics card doesn't store data, I don't see the point. Maybe if you live in the middle of nowhere, and an "emergency" graphics card is days away, sure, I guess. Islanders, 3rd-world countries, rural areas. But it's unnecessary most of the time, easier to just buy a newer/better card.
If you want to bake in the oven, make cookies instead.