Yesterday, I performed 500 pushups in under 20 minutes

[Gerry Seymour]

yup...

i doubt it as there is no real progressive resistance there apart from reps of course but you will get no further size.

There’s pretty good evidence that muscles do get stronger from high reps and low weight, though it’s not optimal and won’t progress as far. Fatiguing the muscles seems to be the necessary factor.