Correct, but that’s not a choice the user has to make. The SMS App of choice decides to send pictures as MMS, so choosing the SMS App to share a picture is the right way.
I can confirm this behaviour with the /e/OS default gallery App on 1.12.3-s-20230616300623-dev-FP3.
However, I don’t use the default gallery App, I’m using Simple Gallery Pro instead, and this works as intended, I just checked.