Hi Diskutant,
The Finder not only does not show any file whose name begins with "._", but any file beginning with these two characters is not tar-ed by Apple's tar command (they are just left out), nor are they copied/transferred by Drag-n-Drop, AirDrop, Universal Control, Cut-n-Paste, nor cp, even when these "._*" files are inside a directory whose name does not begin with "._" and it is this outer directory that you are copying/transferring.
Personally, I would call this a bug.
Fortunately, it turns out the the GNU/Linux/Homebrew version "gtar" does archive such "._*" files (and Apple's "tar" used to do so also, but this changed a few years ago). Also, "rsync" does properly transfer "._*" files, so I always use "gtar" and "rsync" to copy/transfer any directory/file under macOS. Since these files are not recognized by the Finder, I suspect that Time Machine also doesn't back them up, but I haven't tested this as I don't use Time Machine.
A couple years back I tested most all of the utilities for copying/transferring files, such as ditto, dd, cp of an SMB mounted volume, rsync, pax, shar, zip, scp, sftp, tar, gtar, Finder Drag-n-Drop, Cut-n-Paste, AirDrop, Universal Control Drag-n-Drop, Cut-n-Paste, etc. and found inconsistent results with the Finder utilities never working and the other utilities being inconsistent --- thus I settled on using only Homebrew's gtar and rsync which always copied/transferred all files and directories.
Most likely you probably don't care about such files beginning with "._", but they are used in the Windows OS and I have found that some databases and their apps also use these filenames.
Solouki