That’s anachronistic. For example you’d say macOS Tahoe but Mac OS X Leopard and Mac OS 9.1.

And going back a little further, I believe it was "System 7.5.5" etc. until Mac OS 8.5 or so?

I think Mac OS 7.6 was the first to have the branding

the "two face" logo.. the reference was, the logo could be a single face, or a face in the distance with a second as profile in front. IIR

Reflection of the happy user's face on the monitor, engaging in pleasing human-computer interaction.

While we are on the subject it is also worth pointing out additionally:

When saying Mac OS X, it’s pronounced Mac OS ten, not Mac OS ex.

https://www.youtube.com/watch?v=dHrVGk0WwYM

"Mac? Oh, Sex!" is how everyone pronounces it. Very few people "properly" say Mac Oh Ess Ten.

No, that's what perverts do with the Darwin native executable format.