I did some digging myself to find out what the reason could be.
It seems one difference is that “rooted debugging” is deactivated on 1.0-q-stable, but not on 1.0-q-dev (I confirmed this, I have access to a stable device as well)
This issue and the corresponding forum post indicate it was removed lately.
This documentation request further suggests it was done to pass SafetyNet. Sadly, it does not make it clear if this is the only difference, it also mentions “some logs”.
I find it interesting that the sources suggest there are some dev versions where rooted debugging is disabled. While I wish this would also be the case for me (because I (mis)use the dev version as a daily driver 
) I can also understand people who don’t like this, because they specifically chose the dev branch, because they want more control and therefore really need this option.
@mihi What about you, do you have the option for rooted debugging in 1.0-r-dev?
Currently I have no plans to switch to R, I would only need SafetyNet for one App that I can circumvent by pleasing our German bureaucrats with some paper mail, but thanks for the suggestion 