Either way, as someone who identifies as a progressive, I found TGZ's prediction that Biden would pardon Trump and the later stated reasoning to be worthy of an eye-roll and little more. He'd almost certainly be proven wrong, regardless. Biden isn't a saint, either in the past or now, but the factors in play now are notably different than they were in what he's used to try to justify his claims with.
The DoJ bit has a bit of a better foundation - Garland dragging his feet, failing to prosecute Trump for things like the various cases of obstruction of Justice listed in the Mueller Report, the DoJ engaging in delay tactics - last minute infodump as an example IIRC, and so on. Even so, TGZ's prediction seems off. Trump actively weaponized the DoJ to interfere with all cases at all related to him, including at the state level - and it was not ineffective. The same can be reasonably expected to happen again. Under Biden, the DoJ can be expected to mostly stay in line. Under Trump, it can't.