And that's the thing. I read it, and thought "Yes, it could be a coercive threat, or a request for a quid-pro-quo. But it could also be a change of subject." For a normal person, it would be ambiguous. For Trump, who's use of the language is bowling-ball sharp at the best of times, and who's as subtle as a shark in a goldfish bowl, it's that much worse.
Really, to say it in any way proves or even represents coercion is begging the question. It's only true if you interpret it through an a priori presumption of bad acts ("Trump abuses power, therefore this is an abuse of power, which proves Trump abuses power.") . Perfectly solid grounds for impeachment, sure...