Some teams the top threat is in the slot. So yes that is true to some extent.
But the bottom line here is slot is where you put your worst athlete among your cover options. Lacking athleticism is much worse outside the hash. But we saw them do that with Kendrick, because in part you had Ramsey cycling through the slot to boost the run game or when they wanted to protect him. Rams were very aware that he was mismatched vs some of the top wideouts in this league.
This season I expect we'll see Kendrick in the slot. Durant will be outside the hash along with whatever corner we pick in round 2 or 3. We will probably see a safety or corner added later in the draft that can play the slot, as those types are numerous and easy to find compared to the boundary corners. So my bet is one corner early and one late, and hopefully we hit on at least one of the two.