Is that a Multiboot selection on startup?

[jojuma]

I recently flashed the current build from July 2nd on my emmc since I had issues lately after updating.
When I switch the phone on now, there appears a screen showing 'Mobian' which I have to select to continue booting. 

Is that meant to be a multi boot option?
If so, can I omit that screen somehow as long as there's one OS only?
On the other hand, how would I add an OS?

Thanks in advance for clarification