^I actually think Nina got a headstart with Kamala, she may have approached her way before Vogue even considered doing a feature. In the end the Elle cover didn't hurt her profile. Instead people are more up in arms over AOC's Vanity Fair cover and had Kamala appear in or on Vogue she'd have suffered the same backlash because these magazines are considered elitist.
As for Jill having to wait not in order for Vogue not to appear biased, too late for that. Vogue already refused to give Melania a cover for 4 years, and quite right too. Even if Jill gets a cover in the final year of a Biden presidency some will still bring up the fact that Melania didn't get one.
Vogue made a bold decision to get involved in politics, took a stand by endorsing HRC, and continued on that stance. May as well go all the way and bugger the haters.