This patchset (mostly patch 4) increases claws-mail's closure size from 563 MiB to 1128 MiB.

That's a definition of "lightweight" (see revised synopsis and description) I was not aware of.

I'm not necessarily opposed--but for example does it really need webkitgtk ?
What does it do with it ?

(There were really bad security problems in Microsoft Outlook because they
were using a more-capable-than-necessary web browser to render HTML mail,
back in the day?)