Thanks for taking the time to actually say some points rather than "No limits,"

Deflecting the attack nearly exhausted Goku, but Saitama didn't even break a sweat.

The scale of attack was very different as I already stated, wiping a surface of a planet is nothing compared to destroying a planet, and Goku vs Vegeta was far closer than Boros vs Saitama.

The only time we actually saw Vegeta outright destroy a planet before his fight with Goku was in an anime-only filler arc, which in general tend to throw out consistency with regard to established feats of strength.

We never saw a OPM character destroy anything bigger than a mountain either, yet we're accepting that Boros was a surface wiper.

Vegeta has a pretty consistent tendency to drastically overestimate his own abilities. He's exactly the kind of character that would overstate his power to feed his ego.

Doesn't seem far fetched at all, Roshi was capable of destroying a moon back in Dragon Ball, and Vegeta is over 150x stronger than Roshi, while the earth is only ~3.6x bigger than the moon, so mathematically speaking it's more than possible.