I hate how random DB is with lifting strength feats it's so silly sometimes. Toriyama is the GOAT but bro really hated math or something.
Like how does Goku go from pushing a massive boulder as a kid during Roshi's training to using 100 kilograms of weighted clothing as a training method when he's like a million times stronger. How does Goku struggle with 10x gravity on King Kai's Planet when he didn't even notice it as an infant child with a power level of 2 (plus 10x gravity would only make him like maybe 1 ton). And then there's the 40 ton thing obviously.
Buu Saga character's should be able to rip apart neutron stars with their brute strength lmao.
When you look into it, it's not actually random,
From OG DB, their lifting strength has been sequestered into two groups
Normal lifting - basically picking things up, bench pressing, combat applicable
Body weight - wearing weighted clothing/gravity training
.it's somewhat similar t the combat speed and travel speed difference imho
Basically;
1) When Goku pushes the first boulder, calced at about 40 tons, he's also training with 10kg or so weighted clothing
2) When Goku and krillin then push the much larger boulder, (about 300-500+ tons iirc) the train with 40kg weights
3) At the tournament, Goku tosses a Giant piccolo (whose body weight alone was about 160 tons) yet isbweighed down by 250 pounds weifted clothing
4) 40 tons thing was also weighted clothing, but as the data books explained, using bukijutsu with weights is extremely difficult
Then when it comes to gravity, it's treated more as an adaptive thing in DB
1) Goku was born on planet Vegeta yet struggled initially under 10x, he wasn't weaker than when he was a baby
2) post Frieza Gohan, who's thousands of time stronger than any average Saiyan, struggled under 10x gravity when he first experienced it, his lifting strength isn't less than those Saiyans
Super anime is the one that seemed to unite both