Thank you for your answer. But it's not what I want to do, I just want to drag from the email and drop to the open directory of the Finder. Only one action, as I'm used with Apple.
When I do it with in PDF as icon in the email: no issue.
When it's a one pager PDF: there is a image preview of the file inside the email. That's when there is a problem.
Doing many tests I think I may have understood the issue.
1) I have a trackpad not a mouse
2) I'm used to drag and drop doing a soft clic on the trackpad
3) It works perfectly to drag and drop a file under icon in the email
4) But I just understood that if I drag and drop with a soft clic a PDF that is seen as image in the email
- if I clic on a zone with text it selects a small part of text and (eventually) drop a RTF file !!!
- if I clic on the empty part of the image it drops a "inetloc" file
- if I clic STRONGLY (2nd level): it drags and drop the file as desired --> I didn't know that !!!
So in conclusion: doing this post made me understand the way it works... :-)
As I always did this way without any issue, I imagine it's a novelty of lasts update of macOS (appears to me linked to the ability to select something into the image of the PDF).
Before doing this post I made a lot of research without finding anything, so it might not be documented yet?
I also went to your 2 links without finding it. BUT there is an info saying that if you control+clic on the image of a PDF in Mail you can chose to change it to icon instead of image --> I tried but this option doesn't exist in my French macOS 12.3.1, maybe it's not available anymore?
So finally, question answered, even if not easy to understand why this behavior was changed... = for an icon PDF, soft clic to drag and drop / for an image PDF (one page PDF) strong clic mandatory !!
