The method for this is surprisingly simple; the UFO's in the level respawn approximately every 10 seconds and drop 0-3 pons (with a chance for 1 of them to be replaced with a heart pon when missing health) when killed so its just a matter of patients and farming the spawns.

The 'Broken Clock' badge mod allows for even faster spawns to make this possible in a reasonable amount of time.

To my knowledge this isn't possible in the other levels that use the score mechanic as Murder on the owl express and The big parade dont have any enemies to farm. Train rush does have a few enemies at the end but the time limit makes farming them impossible (and pointless as seconds remaining is worth more score than pons).

Is this intended? no. Should it be patched? also no.