There are styles of music where the lyrics do not matter. Students that I taught, who were proponents of the harder end on the 'Metal' spectrum would regularly mix both recordings and live performances with what I would call the 'lead vocal' at a lower level than the chainsaw distorted guitars- which cause frequency masking in any case.
To me that was a bad technical mistake, but back to back comparisons with commercially recorded tracks submitted as targets showed that inaudible vocals are regarded as part of the genre. The extreme case would be the screamed or grunted vocals often used- clearly meant to be incomprehensible!
The sound that such producers and engineers achieve in this way represent,for them,"energy". A conventionally mixed track with vocals clearly upfront, and EQ levels set to create separation between guitar and voice is thought to lack 'guts'.
I know the Levellers are not Death Metallers, but they are a high energy outfit. If the sound engineer had been given that phrase as a guideline for his mix, the result could well have been as described.
'Blame the sound engineer' is easy to do, but the vast majority of the many sound engineers I know, do exactly what is asked of them- however much it hurts them to do it.
Cheers
Dave