I don't want to hijack but, if that is true, why do the manufacturers recommend a 450w power supply?
Might as well ask why do Ryzen processors come with coolers that aren't capable enough to keep them cool without driving you insane with the constant ramping up and down, up and down, up and down.
Might as well ask why do hospitals and doctors send people home telling them they are fine and to simply get bed rest, and then those same people die of any number of conditions the next day.
Or why dealerships and tire shops tend to under-inflate tires.
And, as DSzymborski alluded to, because the more they influence you towards buying or having a more expensive power supply, by recommending higher capacities, the less you have to spend on their product OR the less likely you are to buy their product in the first place knowing that you really ought to have a more capable PSU before doing so. As I said, you can run any number of graphics cards on power supplies that minimally cover the requirements of the card, but does that make it a good idea?
I mean, technically speaking, you can drive around for months on the temporary doughnut tire that most vehicle manufacturers include with the vehicle, but it's a REALLY BAD idea to do that, or to leave it on for any longer than it takes to get somewhere where you can get a reliable replacement. Manufacturers primarily concern themselves with two things. Profits and liabilities. Saying you need a 450w unit only when a 550w unit is an obviously safer, saner and overall long term better option, covers any liability concerns because technically 450w is enough, even though it might not be based on the specific unit in question. That part however is not the manufacturers problem. If you choose to get a unit that isn't good enough, that's your problem, not theirs. Same thing if you have to live with a fan that is constantly running at high speed because you are running near that capacity on a regular basis. It works, and they don't have to hear it, so it's your problem.