I don't see that to be a common occurrence, where it's an evenly split ratio. I've seen and heard so much of instances where there ends up being one seke who wants to predominantly bottom. And damn straight you are and will be... not that you could even top me in your dreams.
I've come across some partners in the past that are great, and same mentality with fairly sharing roles as true sekes. I always make it very clear I'll have none of someone saying 'oh I'll do a seke pairing' and then try to really just be the bottom all the time.
I remember reading something along those lines in that request thread of yours, way back. Immediately thought "well, that won't be issue since no way in hell am I going to have a bottom main character" and continued on browsing until I saw that idea of yours and I wanted to snatch it, before some wannabe seme or seke did.