I think that's not intended. Tried a mossy shield on a Krong altar, message said he's pleased, there were no stats in the message and the stats didn't change either
I've had this happen with at least 4 times on 3 different shield types. I stopped putting shields in there.
And as an addendum, it may just be a display bug, but the message behaves kind of oddly when you enchant something already enchanted. Say I put a wooden sword in there and get +1 transmutation damage as a buff for it. Then I find another altar, it will often (but not always?) say "+1 transmutation damage, +2 radiant damage" and I'll be all "woo, that sword is up to +4 total now!), but no, I think it's just redisplaying (or replacing) that original +1 transmutation damage buff, not stacking with it.
sad but true. i have had this happen as well on a few items... that is why i always run a save and continue before i place anything on an anvil... it also lets me go kill myself and retry again if i get a 'displeased' message and wreck my gear. LOL