Ok yes i see what you mean,nothing i,ve seen on the net clarifies that.
Logically id expect the system to read the two os seperately and be ok but having not done it i couldnt say for sure.
Id suspect you,d be ok but thats not really definintive enough when your system and data,s at stake is it.
I guess you could make a system image of the 7,then try it and see what happens.
Also might be worth posting the question (with a very clear explanation in the subject header):-) on the Windows 10 forums,some knowlegable people there.