That is correct. A defendant generally only gets a reduction for accepting responsibility if they plead guilty, except in certain situation where they plead not guilty over a matter of law such as a Constitutional challenge. Acceptance of responsibility is based on primarily on pre-trial statements, not remorse shown only after trial and conviction.
And on this, it really must have been a gambler's decision for Weinstein and his lawyers. After all, they had three potential options in the NY trial:
1) Plead guilty to all charges pre-trial and make the strongest possible appeal for clemency from the sentencing judge;
2) Agree some form of plea bargain with State prosecutors, pleading guilty to a lesser set of charges, and appeal for clemency in sentencing (and this option would only even be possible if the State were prepared to accept a plea bargain in this case....);
3) Plead not guilty, and allow the charges to be tried by a jury - with the understanding that if the jury returns guilty verdicts on any of the charges, there's a higher likelihood of harsher sentencing on these convictions.
Given that Weinstein and his lawyers have long known that further criminal charges are pending in California for similar-pattern (alleged) offences, I'd have thought that both (1) and, to a lesser degree, (2) would be highly risky strategies for the NY charges - because they'd very probably make the likelihood of convictions in California a lot higher (assuming the allowance of similar fact evidence).
So in reality, Weinstein & lawyers probably knew that going down the (1) or (2) route would lead to probable significant jail time in NY, followed by significant jail time in California. I think that, from a pure probability-expectation perspective - based on the reasonable opinion that convictions on these NY charges in a jury trial were very far from guaranteed - the least-bad strategy was to fight the NY charges in court (as indeed he did). And after all, if he'd beaten all of those NY charges at trial, it's possible that California might even have reconsidered whether to charge him at all (but even if they did charge him, his NY acquittals might well have helped him in any CA jury trial).
So, in my opinion, Weinstein actually had little option but to gamble by protesting his innocence and putting the charges to a jury. The gamble very slightly succeeded (inasmuch as he was acquitted on the two most serious charges), but taken as a whole, one would have to conclude that the gamble failed.