I mean Pence had to turn them in to be radified last time, does Harris not do it now because some weird rule? If it's not her I assume it would be Johnson and he might try to deny them.
Congress (back when it was functional- you know, when the Dems were in control) passed a law codifying the VP's role in elections is only to certify the results. So in theory she wouldn't be able to question it the way Pence could have (though as I understand it, even the idea that Pence could have delayed cert was on shaky legal ground, but at least now that ground has been completely knocked out).
Ethically, you'd expect that since the VP is running for President that she'd step aside of the process and let the President Pro-Tem handle it (unlike Georgia's current governor, who was secretary of state and refused to recuse himself from his own election) though I don't think there is any legal requirement for her to do so.
I don't think they wanted Pence to delay anything, they just wanted him to declare the fake electors as the real ones to be certified as correct. They were as close to stealing the entire country as just having a lie. Any investigation could have been squashed by the residing president, like Muller's investigation being cut short. And him pardoning multiple Russian tied cohorts.
Why? Al Gore and Richard Nixon both certified their losses, while Bush-41 certified his victory, and every year that the incumbent ticket wins is a year that the VP certifies their victory as VP. What's so different now? Frankly, nothing.
The reason she won't is because of aggressive redistricting and roll purging by de santis. The polls are of likely voters. The thing about roll purges is it means people who thought they were registered to vote won't be able to.
In fact most states in which trump's minions have established control over the election apparatus will have a strong red shift away from the polls.