Still the pure count is more or less 50-50 (9 to 11 and 3 sport series, Sengoku is hard to go, it's kinda action but still a historic manga, not so loose on this term like Mushibugyo). I said, that it was simple generalisation... Just like JUMP=BATTLE, MAGAZINE=SPORT (please don't take this too seriously). Sunday first big action series that actually hit was Ushio to Tora or Kenji, though dunno if it was big enough to count it. Ushio started in 1990. In 55 years history, only after 30 years, they had series like this become a hit. Of course there were Cyborg 009, but it was tossed around. Second, thing I really didn't say that they aren't important part of the magazine, but for Sunday by no means there is a bigger push to have hit action series. They focus more on the relaxing series which doesn't exclude second statement, they try to minimize the effect by putting action series mostly by more experienced mangaka, when mangaka from their workshop, mostly do lighter mangas. Even on the TOC you posted it gives this away, (with Kenichi and Kekkaishi being first hit series for both mangaka, and rest aside Kaito is done by more experienced mangakas). This also don't exclude that they don't try their youngsters to do action series (Dejikon, Drea-Mer, Kirwo).
The times for Sunday starting from 2000, were just lackluster. It was this times that Sunday tried to change and failed so miserably. Thanks to actually hitting with action series (Gash, Kekkaishi, Kenichi, Inuyasha, Arms, Recca, Mar and smaller) they tried to push more and we could say that this times where the (around 2004 to 2009-11?) times when action took main role, STILL this times were the worst times for Sunday. They had the biggest jumps in circulation, when their rivals still didn't go with drops, they had lower numbers of mid popular series, their older mangaka went to do series in seinen magazines, in 2005-2008 biggest published series was Zettai Karen Children and probably nothing more came out.
Last thing here, when we say Sunday, do we really think of all this action series? Or is it more Rumiko and Adachi? Sunday is remembered because of them and when there are series like this, they are kinda compared to Rumiko and Adachi works. They were precursors in those genre, that's why relaxing series (koushien love story and romcom) is something that was stuck to it. Just what Toriyama is for Jump, thanks to Dragon Ball.
Ehh, that's the only thing I can go to compromise, or rather to just develop my opinion or just what I meant. This talks were done (if my memory works right) in the right thread for it, not here. Sorry for mistakes, it's long so probably there are few.