Welcome, JayZeeP, to Apple Support Communities!
Those are interesting results.
As one can verify, by simply performing the definitive test found in my comment at https://discussions.apple.com/thread/251807601?answerId=254806789022#254806789022, «pictures» are always sent as «attachments», regardless how they may appear (formatting of any email client).
There simply is no way to actually «embed» «pictures» in an email (not while being Standards compliant, which Apple demonstrably complies with). All that can ever happen is that the «attached» «pictures» are formatted inline with whatever text there may be as a part of the email.
Unless appearance is the only concern (seldom the case, and doesn’t appear to be the case with you), all email clients—with the exception of that very tiny subset of email clients (apparently consisting of a single email client and its derivatives)—allow users to perform bulk attachment operations (such as bulk-saves) regardless how they may display the «pictures».
Unfortunately, that very tiny subset of email clients (apparently consisting of a single email client and its derivatives) prevents its users from performing bulk attachment operations (such as bulk-saves), except under a very narrow subset of email compositions, subject to its own, hidden criteria.
Additionally, the email clients in that very tiny subset haven’t improved their International Internet Standards (governing emails) compliance in over a Decade.
Only that company can truly fix this issue with their email clients.
What you have found appears to be a rather interesting “workaround”, but, since it doesn’t actually fix that very tiny subset of email clients, it will, almost certainly, be very fragile: subject to being easily broken by any tiny changes in the web of interactions involved in transferring emails.