It would tie the hands of the next jury because they would not feel free to ask the judge certain questions during deliberations, lest it be taken as a verdict. The verdict is rendered after all deliberations are completed, minds can be changed, that point was never reached here.
In what way would future juries' hands be tied if there were a requirement that if the state wants to retry a defendant on a particular charge following a hung jury, it must be able to plausibly claim that the jury would have been unlikely to unanimously acquit the defendant for that charge if allowed to do so? The state could easily meed such a burden going forward by having at least one juror to go on record as saying that. Note that the juror(s) going on record would not have to identify themselves (nor anyone in particular) as being the reason that the jury wouldn't acquit. If any juror is holding out for conviction, and if all twelve jurors are honest, the jurors should unanimously agree that there was at least one holding out for conviction. Even if some jurors might dishonestly claim that they were all willing to convict, even a single claim of non-consensus would be inherently self-validating.
Even if states haven't gone through the trouble in previous cases of putting jurors on record as saying that at least one was unwilling to acquit, it's reasonable to presume that--absent evidence to the contrary--hung juries were a result of at least one juror's unwillingness to acquit. In the case at hand, though, there exists evidence to rebut that presumption.