When HTTP basic auth is done over HTTPS, the warning that would be shown for sending a password over plain unencrypted HTTP appears. Safari's behaviour is correct - if HTTPS is being used, the login information isn't being sent unencrypted.
Orion and macOS:
Version 0.99.109.1.2-beta (WebKit 613.1.12)
Image/Video:
Orion behaviour:

Safari behaviour:
