I think we can describe it all from Harry's side in one phrase: "I thought this was going to be a standard PR relationship, but it's gotten out of hand". I'm sure neither he nor Florence expected that.
I see what you mean, and I agree, with one small caveat:
Whenever Harry is in a bold transition period in his career (One Direction breaking in to the US market, Taylor; becoming a solo artist, Kendall; breaking into Hollywood, Olivia), his stunt partners have always been much more high profile than "the usual" so in that sense, I believe he knew that it wasn't going to be the standard "have dinner, share a few jackets, get two pap shots and bounce" situation.
What they never seem to account for is the higher profile stunt partners' personalities and how they fully intend to use the stunt not only to their advantage but to ensure they are (and will remain) in the spotlight, for years to come. We were relatively luck with Kendall, as she seemed to be content with her own level of fame and current fanbase.
And, that's all I'll say about that.