Even if this is a bug in the HD mod, without it, other bugs appear with gray Castles, duplicated heroes, etc. In the Novosibirsk game, Napalm vs. PReDS, I was exhausted trying to fix a gray Castle. How can I fix all the bugs and get a stable version?

You just need to call things by their proper names. Your desire to throw shade at VT at any convenient (or inconvenient) moment is annoying, but in this case, it can only be described as spreading knowingly false information. Although the problem itself certainly exists.

It makes sense to ask the developers of VT and the HD mod about solving this problem, which I am not. My view of the situation is this: since the HD mod is an extension of VT, the first step should be to send a detailed description of the bug with save files to Baratortch. If, as previously stated, he has refused to support all versions of the HD mod based on WoG, then the only option is to abandon the idea of using the HD mod for VT and do as Lizard suggests above. That is, only fix the duplications.

If, in fact, this error with different terrain is the only one, then the VT developers can also try to fix it. But where is the guarantee that new incompatibilities will not appear in the future? And it will be problematic to fix them on the VT side each time.
In my opinion, the ideal solution is to integrate a module into VT to fix duplications, similar to the HD mod, since the rest of the HD mod's functionality is of little use for VT. Password-protecting saves is another option, but it is easier to implement.

As far as I understand, no attempts have even been made to submit a proper bug report with save files.

So, at the moment, you need to choose a version from what is available.
For me, for example, VT is definitely preferable, even with the existing bugs. Also, if there is an interest in improving the VT version, offer your help to the developers in fixing the bugs; I don't think they will refuse