+EV call otr is a mix call/fold?

Hi all, theory noob here. In a river spot, GTOWizard says my call 100bb deep on kq210hhhh8d vs a check shove with Ace of hearts is +6 EV but still says to fold 50% of the time. Surely if it's a plus EV call I should call all the time? I'm definitely missing what feels like a fairly important concept here as this situation occurs in other spots as well, can you help me out?

I kind of get how somehow you may make a -EV play to protect other parts of your range and extract value over the long-term when you have other hands, but in this call/fold scenario otr I don't understand that logic.

My other thought is that if you're indifferent between calling and folding, the EV should be 0 for both calling and folding, not the case here according to GTOW.

What got me into this situation if you're interested was this hand: https://www.youtube.com/watch?v=vMu_UbNz.... In this hand, villain needs to find bluffs with some random 2p and 9h to call with the Ace of hearts.