the main reason I can think of why china would develop a Dedicated fighter bomber is if she perceive a need to sustain a large number of sorties to a range considerably farther than J-16 or J-20 can reach, and do so without refueling. It would be prohibitively and unnecessarily expensive to build up a fleet a strategic bombers large enough to do this.
I think such a need is not only there, but quite pressing because I think such sorties can become the mainstay of chinese sustained sea denial operation at the edge of second island chain and beyond. And it would take a lot of sorties.
Keep in mind stealth is good, but speed is still an effective way to To complicate enemy interception efforts, and degrade effectiveness of enemy air and surface based air defense assets. So I will not be surprised if the The Chinese try to develop some thing that has combat radius intermediate between the J 20, and the H 20, and is built more like a fighter so as to be able to supercruise