Well, finally I got some kind of answer.
After days of waiting, and after sending the suspected files to Avast (from Avast Chest), the files were identified as FP.
But I can learn several additional things from this experience.
First, the zip archive where the suspected files came from is "broken". Once a file inside the zip was "extracted" by Avast so to put it in the chest, the zip was altered. THIS IS VERY VERY BAD.
Moreover, after the files were "cleared" by Avast (in this case, since they were FP), I couldn't restore the files to their original source (inside the zip). THIS IS VERY VERY BAD.
In addition, since the files were finally identified as FP, I have a "kind of answer". I mean, I had no idea if the files were actually received by Avast Team, of if they were checked. For days, anything was possible. Maybe the files failed to get to Avast's server? Who could know? I had no way to corroborate the status of the process.
If the files were NOT FP's, then I would had *never* seen any change, any response, any kind of knowledge about these files. They had been stayed in the chest with no kind of positive or negative answer/confirmation.
In conclusion, the most basic response I have is somehow random: my files were FP, then I had luck and after several days they were cleared. I am thankful to Avast Team for this and for the program.
The most important conclusion is that the process, the communication, from the point of view of the simple user, is based on luck (although, to be fair, not only on luck). The only way I think is available to the user is to come to the public Avast forum and specifically ask for some kind of response, in hope that someone of Avast Team can answer directly through the forum.
In the middle, I have to keep in mind for the next time not to allow Avast to send anything to the chest that comes from inside a zip or any kind of archive. It is much better to block it, temporarily put the specific location as exclusion, expand the archive, then send the specific files to the chest, and restore the exclusions to the previous state.
I hope this experience can help other users, and specially that can help to improve Avast for future versions.