You can non-explicitly enforce positive review coverage by simply not sending review units to people who are likely to say things bad about your products. If you send early review units to 10 people one year, and the next year only 6 of them get review units, and the 4 people who didn't get review units this year were the 4 who gave the harshest review, the message is now out that you need to say good things if you want to continue getting early access to devices for reviews.
SnazzyLabs is a good example - he should be well within the criteria for Apple to be sending him iPhones and Macs early, but I can only assume Apple thinks he's too critical when he finds an issue he doesn't like. Thus he has to buy his review units on street release date along with everyone else. How many people are giving less critical reviews because of that?
nVidia tried to pull this stunt with the YouTube channel Hardware Unboxed. They weren't singing the praises of RTX and DLSS loud enough for nVidia and were threatened with having review samples withheld until they changed their tune.
So if I style myself as a negative only reviewer, they have to give me a review unit? Like I'm that judge in the olympics that never gives anyone a perfect score. The best your product will get from me is a 2/10.
I would guess it would be more lie your solicted reviews should not deviate significantly from you unsolicited reviews. Perhaps there will be a market for "negging" reviewers? Those who criticize but only in the ways that don't impact sales?
SnazzyLabs is a good example - he should be well within the criteria for Apple to be sending him iPhones and Macs early, but I can only assume Apple thinks he's too critical when he finds an issue he doesn't like. Thus he has to buy his review units on street release date along with everyone else. How many people are giving less critical reviews because of that?