they already are a couple
No- they are a real couple when one says please go out with me / be my girlfriend- and the other says yes - and they start kissing etc. Sure it looks like they both want to be - especially Haruka- she is knowingly actively persuing kanae - but im unsure if Kanae knows whats up yet- she might not of thought about about it.
You know not every couple goes through the whole confession/asking out thing. Some poeple just get together. They mutually realize what they've got going and just go with it.
Yeah- sure, sometimes. . And after they realise? They start to act like a couple - kissing etc.. and will acknowledge it with each other.. and these 2 are NOTthere- not yet. They are acting like a couple who are into each other / persuing each other etc - or at least Haruka fore sure is. Also no way the author is gonna hook them up off 'screen' imo.
They also say stuff that reveals they are NOT yet a couple - like saying 'I didn't realise you liked me so much' and blushing.. She wouldnt be suprised by her calling her HER Haruka if they were a couple.
My friend, I'm the guy who caused a stir before by saying that I wasn't at all convinced that Honoka "confessed" to Elisha in Chapter 250. I'm still not. The word "love" has many facets and degrees, and to me Honoka is obviously (primarily) straight. Please everyone, don't flame me over this again; I'm just making the point that I'm not easily taken in by the "three little words" and have a higher bar for when I believe people have reached yuri couple status.
That being said, even I have trouble seeing how Haruka/Kanae aren't there yet. I hear what you're saying about kissing and other overtly romantic gestures, but we should be careful not to project Western cultural standards onto Japanese teenagers. Despite what manga and doujinshi might have us believe, Japan is still a far more conservative society than what we're accustomed to in the West. The fact that a couple is only at the hand-holding stage and isn't "hooking up" doesn't necessarily mean they aren't a couple.
As for Haruka's "since when have you been that into Haruka" remark, I think that's just a bit of insecurity combined with embarrasment. Remember, up until now, it's been Haruka who's been the posessive one, and who probably sees herself as the one more in love. Kanae's affection has been more subtle and reserved, often coming as a reassuring reaction to Haruka's fears about being overbearing and smothering with her crush. This was the first unmistakably overt display of jealousy and, well, romantic/sexual territoriality shown by Kanae (but not the first display of sexual interest -- see the "Venus Dimples" chapter).
I would recommend re-reading chapter 222 (which came after Haruka's "I Love You" note to Kanae). They're only being mildly subtle here, talking about "the one you like" and "making my heart pound", the latter being an extremely common trope for romantic attraction. I think they're both very much aware of how the other one feels, especially now. How they handle it physically and verbally is a bit beside the point.