So the manga is admitting that Sumika is at fault for why they aren't progressing. Well as long as the author is aware of character flaws (both Sumika and Ikuma's) and doesn't try to pass it off as a "cute quirk", then I think people should not complain whenever Sumika (or Ikuma) does something that prevents the main couple from consummating their marriage.
Any third party interference may be a different story.