Well….perhaps…however, knowing wizards, Lenamare was probably far more concerned about Tom sticking around and munching on Zilquar’s people.
He did immediately turn around and started returning, he just delayed, and then things caught up to him…
So I, myself, would likely have interpreted the “immediately” as deliver the message and don’t stick around, head right back home.
So, he immediately began returning, however, the real constraint was the time constraint of when he had to be back by, and Tom felt that he could
stop for a bit and still return by the time constraint, and technically he could have, he wasn’t lying to himself, if he had been, he couldn’t have stopped.
This is why giving demons instructions is always dangerous. Instructions are often up to interpretation, if the demon can figure out a way to sincerely and “truly” believe they are abiding by the letter of the command, they can generally get away with it. However, they have to convince themselves, legitimately that they are obeying a reasonable interpretation of the command.
Now, that being said, the wizard might disagree, and when the demon gets back and the wizard is ticked off, the wizard can then punish the demon with lots of different torments and punishments. An experienced demon would have been aware of this as well…Tom, probably not so much.