It really doesn't matter where Gintoki and Ichigo are placed, in all fairness. WSJ's probably not sure where to put them either.
I find the newer big series more interesting. Haikyuu!! sells a butt-load more than Soma and BnHA but has never been actually promoted to the big spot. BnHA is less than 40 chapters old but is already being showcased as a potential big one (which it totally is).
Koro-sensei is almost placed in a sorta awkward position in these joint covers, even though his size in such issues is only second to Luffy. I assume thats probably because WSJ knows AC won't last that long.
Edit - Also, I'd say Toriko is pretty unstable. It's following almost the exact same pattern Bleach did. It'll be interesting to see where Toriko would be once this oscillation of ranks stop.
Kochikame is the veteran that never graduates.
Made me laugh more than I should have.