- A reference guide and manual in Russian for Heroes 3.

Actually, there is such a glitch, but the reason is different. The laws of logistics still apply. The trick is that, under certain circumstances, the hero's move reserve (initial moves) is not updated. It should be updated whenever the hero's creatures are rearranged, but sometimes it doesn't. I know for sure that scripts for transferring creatures using Alt+Click (or dismissing them from the main game screen using Alt+Shift+Click) do not update the initial moves. This might also be the case in HD.
The point is this:
We were on a swamp, for example, with a speed of 9. We received a Gnoll (via a transfer script), and the initial moves were not updated, so the calculation of how far the hero will move on the next turn is based on the swamp. Naturally, this is not correct. To always be sure about the range, go to the hero and simply rearrange any stack. Exit, and you will see the correct range. By the way, you can observe this in HD - there is a record of the move/initial moves - use this to see if the initial moves have been updated or not.

I found a save - ND mod - rechecked - it seems to be exactly this situation (now, and in other cases). The point is this. When exchanging armies, they are often rearranged. So, if you don't change the units' positions, but only add them, everything is fine, you can even split them into single units. But if you swap different units before the hero's turn begins, a recalculation will occur (taking into account the unit's speed and the terrain penalty). Therefore, to avoid this, the army should be regrouped after the movement has begun, and not before, and even better - before the battle (or at the end of the turn) - the recalculation seems to occur at the end of the turn and is not very noticeable. However, in my case, I noticed the following. If the hero spent the night on a swamp with a Fly in slot 7 and an Imp in slot 1, there was no penalty in the morning, but if it was the other way around, or if I made a rearrangement, there was a penalty (the turn was reduced). At the same time, for another hero with 7 creature slots, 3 races on a swamp, regardless of the rearrangements, both before and after spending the night, the turn did not change (it was minimal).