I've noticed a surge of testnet blocks over the last few days, and apparently the difficulty permanently got reset to 1 around block 000000000002949f844e92645df73ce9c093e5aac0d962a0fa13eb076eec835c

I know it should go to 1 temporarily if there are no blocks mined for 20 minutes, but i wasn't aware of it being able to go to 1 permanently like that.

Further looking back reveals that this happens periodically. I.e. the previous one was at block 000000000007682725067b780feccae8143ae2a2b771639630f4d5b44b8548c1.

Is this a specific rule on the testnet - difficulty getting reset to 1 every now and then?

Or is it some sort of an effect from too many 20-minutes-late 1.0 blocks? The latter shouldn't be possible, since difficulty can't change by more than a factor of 4 at a time.