unique exceptional drops + possible item bug 3.1.1

[bebo]

are they calculated like normal monsters?

ie is it convenient to keep wormtongue alive until very deep dlvls?

as a side note i'd like to ask if boots of elvenkind have been improved in 3.1.1 or if it's a bug - i found a pair with +4 stealth, +4 speed, feather falling

i'm asking because in the knowledge menu in the description they are not listed to have the possibility of speed bonuses nor other random abilities - up until now if i remember well i only found them with stealth bonuses