I’m not missing a thing, SCamp1575.
This issue is, most definitely, not an attachment vs. “embedded” or “inlined” or “in the body” issue, because, in all cases, regardless the format of the email, or how it is displayed (rendered) by any particular email client, it is an attachment, pure and simple, as it has been for something going on four (4) decades, now.
Note: if you send the email through almost any other email server (besides a Microsoft Exchange server), the resulting email, on your Microsoft Outlook email client, will allow you to bulk-save your attachments (pictures). Otherwise, Microsoft Outlook will disallow you, the user, from performing a bulk-save of your attachments (pictures).
This is actually a Microsoft Outlook issue, not an Apple issue.
Sure. There was a change in how Apple Mail creates and/or transfers emails to SMTP (Simple Mail Transfer Protocol) servers.
Perhaps there is a newer SMTP standard, that Apple has adopted: such changes occur. (Microsoft is “notorious” in not adhering to standards.)
Regardless the change that triggered the resulting change in behavior at the Outlook email client, there would have been no issue, whatsoever, if Outlook would simply allow you the same privileges, with your email attachments, regardless how Outlook chooses to render (display) your email messages.
On the Apple side of the “equation” you could request, by way of Apple Feedback, as you and others have suggested, that Apple provide users an option to create authored emails as plain-text, as I’ve seen in some email clients. Note: plain-text email has been going the way of the “Dodo” for at least a couple of decades, now.
However, at this time, there is no guarantee that this change will affect a solution, in this matter.
(If there was a change to a newer Internet email standard, Apple will not back out of that change.)
On the other hand, all it would take, to solve this issue—guaranteed—is a long overdue update to Microsoft Outlook, to allow users to perform the same bulk attachment operations, regardless how Outlook may choose to render any given email!