I think your assumption about transfiguration is slightly incorrect. Mad Eye Moody turns Draco into a ferret in Goblet of Fire, and states that he is teaching. If Malfoy did not retain his human level intellect while as a ferret it would not have impressed any lessons on him, and other then being slightly sore coming out of the transfiguration would have completely missed the feelings of helplessness that he was in as a ferret.
“Not you — him!” Moody growled, jerking his thumb over his
shoulder at Crabbe, who had just frozen, about to pick up the
white ferret. It seemed that Moody’s rolling eye was magical and
could see out of the back of his head.
Moody started to limp toward Crabbe, Goyle, and the ferret,
which gave a terrified squeak and took off, streaking toward the
“I don’t think so!” roared Moody, pointing his wand at the ferret
again — it flew ten feet into the air, fell with a smack to the floor,
and then bounced upward once more.
“I don’t like people who attack when their opponent’s back’s
turned,” growled Moody as the ferret bounced higher and
higher, squealing in pain. “Stinking, cowardly, scummy thing to
do. . . .”
The ferret flew through the air, its legs and tail flailing helplessly.
“Never — do — that — again —” said Moody, speaking each
word as the ferret hit the stone floor and bounced upward again.
“Professor Moody!” said a shocked voice.
Professor McGonagall was coming down the marble staircase
with her arms full of books.
“Hello, Professor McGonagall,” said Moody calmly, bouncing
the ferret still higher. “What — what are you doing?” said Professor McGonagall, her
eyes following the bouncing ferret’s progress through the air.
“Teaching,” said Moody.
“Teach — Moody, is that a student?” shrieked Professor McGo-
nagall, the books spilling out of her arms. “Yep,” said Moody.
“No!” cried Professor McGonagall, running down the stairs and
pulling out her wand; a moment later, with a loud snapping noise,
Draco Malfoy had reappeared, lying in a heap on the floor with his
sleek blond hair all over his now brilliantly pink face. He got to his
If we assume that Draco did retain his intelligence, then it seems that its not weird for Krum to also retain his intelligence.
again we see Nevile turned into a canary, and appears to retain his intelligence through the experience, as he comes out laughing, instead of dazed and confused.
Just then, Neville caused a slight diversion by turning into a
“Oh — sorry, Neville!” Fred shouted over all the laughter. “I for-
got — it was the custard creams we hexed —”
Within a minute, however, Neville had molted, and once his
feathers had fallen off, he reappeared looking entirely normal. He
even joined in laughing.
“Canary Creams!” Fred shouted to the excitable crowd. “George
and I invented them — seven Sickles each, a bargain!”
We also know Human Transfiguration is a NEWT level skill, while the students already knew non-human transfiguration at grade 4.
“Of course, the ideal solution would be for you to Transfigure
yourself into a submarine or something,” Hermione said. “If only
we’d done human Transfiguration already! But I don’t think we
start that until sixth year, and it can go badly wrong if you don’t
know what you’re doing. . . .”
Hermione's idea was also some form of human transfiguration to give himself what he needed.