I don't see how the shorter wheelbase answer works.
To make skidding easier less friction is required between road and tyre.
Friction is proportional to the force perpendicular to the surface.
On a really long wheel base bike, the reaction acting through the rear wheel is decreased and so it is easier to skid.
This can be seen by riding a tandem with on one on the back, you can skid really easy.
Using this we can say that it is actually easier to skid on a longer wheel base slack geometry road bike. So your inability to be able to skid your conversion was a skills thing.
It's down to skills.
I don't see how the shorter wheelbase answer works.
To make skidding easier less friction is required between road and tyre.
Friction is proportional to the force perpendicular to the surface.
On a really long wheel base bike, the reaction acting through the rear wheel is decreased and so it is easier to skid.
This can be seen by riding a tandem with on one on the back, you can skid really easy.
Using this we can say that it is actually easier to skid on a longer wheel base slack geometry road bike. So your inability to be able to skid your conversion was a skills thing.