Not sure if that's relevant for the American/Canadian market, but the cover came as standard on my EU 2023 V60CC (it's an Ultimate, but I never noticed it could have been missing had I opted for a lower trim). Must be a market-specific change (decontenting?) that Volvo made for some reason.
I'm similarly disappointed in the lack of a hood insulation mat (luckily the B5 is nice and quiet). From Volvo's perspective those few dollars saved here and there surely add up at scale. I know Volvo is not alone in doing this, but it's a shame nonetheless.