Yes, I was thinking the same. A default set to ‘all’ and i think the minimum set is frontier plus 1 so maybe the value set is for the additional blocks on top of the minimum set.

So:

-1 = no pruning

0 = full pruning

1 = frontier + predecessor + 1 additional predecessor

2 = frontier + predecessor + 2 additional predecessor

Hoping that this and new PoW or floor difficulty increase gets prioritised.

Out of interest, whats stopping everyone trimming the ledger and losing old block information such that its hard to bootstrap in future? Will we need to use node telemetry possibly to determine if people can all prune?