Along with what max silver said, Biggio was also a rookie who was a tad older than your usual top guys. The projections simply see him regressing to the mean, it's not common for rookies to post such an excellent walk rate as he did while striking out higher than in the minors with good power. Projections tend to be conservative, so they regress Biggio to be closer to the average second year 25 year old player with similar hitting profiles, while also not expecting him to be an elite baserunner.
On the other hand, Vladdy who torched the minors but was disappointing in the majors is expected to regress to his mean, which is a 21 year old hitting force to be reckoned with.
It should be noted, Statcast and UZR vs. DRS see a vastly different defender. UZR and DRS thought Biggio was average to below average, while Statcast rated him as a near elite defender, 92nd percentile in the league. It's very likely if our internal evaluations follow a model closer to Statcast's, which I would assume is the case, that the team likely valued Cavan as closer to a 3-4 win player last season and would likely project him to be in that range as well, with some regression factored in.