The loudness and compression on Low's last couple of albums is very much deliberate, so it's surprising that the vinyl doesn't have it. Though I heard similar claims about Sleater-Kinney's The Woods, which was also intensely compressed for artistic effect.

This. The loudness is an aesthetic choice.

The reason it was backed off for the vinyl master is most likely due to physical limitations of the medium. If the audio channels are too loud (wide) there is risk that the needle will jump out of the groove.

There's compression and distortion for sure on the vinyl, but when you look at the waveform on the digital it's right up to the max. It completely changes the sound.