Gnome themes for apps installed in .themes don't work for bizarre dimensions in bars and icons. Can it depends on gtk issues?

Hi all
I'm using Ubuntu 20.04 and as usual I have downloaded some themes frome gnome-look.com but only a few of them really work.
I've followed the installation instructions to unpack the themes in my home/myname/.themes directory.
Than I've used Gnome -tweaks to install them.

What os the cause of this behaviour? It depends from a GTK issue or other?
Thanks in advance.
Enrico Dini