Even if shoujo manga generally have more pages than shounen it only has few more pages.
If the mangaka work harder they could release it weekly .
But that probably would exhaust them .
Shounen mangaka work on 17/18 pages for a chapter every week with only a rest once in a while (golden week or holidays)
(sometimes also after a arc finished or after bigger chapters like end of arc or specials)
But most of the time shoujo manga has more details in it .