I did some more testing and the issue is with the WP User Avatar plugin.
When that is active, the classnames added by the Views shortcode are lost. De-activating that plugin, the wpv-profile-picture-shape-circle class is added to the image.
So, in terms of whether there are other things affected by the issue I would say that the effects are likely limited to the classnames on the avatar, for which we have a workaround.
I could ask my colleagues to investigate the root cause, but I don't think it would have a very high priority.
Okay. But your colleagues should think that, since you do not provide a system to manage the image of the avatar, you force to use other systems, and as you advise using WP User Avatar, so logically you should perfectly make this plugin compatible with Toolset.
Thanks for your help Nigel and Merry Christmas.