I think the biggest difference here is seen when comparing to a single-core mission, such as Starlink 5-1. The boosters of a Heavy are pushing a much greater load (almost half of a full Falcon 9 each) than the booster of a Starlink. As a result their acceleration tops out at 2Gs, and their speed at cutoff is much less (maybe 1500 m/s as opposed to about 2200 m/s, reading from the graphs). The boostback burn helps even more, cutting the horizontal component roughly in half, since they take about 5 minutes to return where they spent 2.5 minutes going out. As a result their boostback burn starts at about 1300 m/s and drops them to about 1000 m/s. This is a quite short burn. Then the slow speed means the aero deceleration is less, too, about 3.7 Gs peak.On the StarLink missions, the entry burn starts at about 2200 m/s and ends at 1500 m/s. That's more than twice the dV needed and explains why the entry burn is twice as long. Then the higher exit speed from the burn means stronger aero deceleration (looks like about 5.8 Gs). So FH side boosters have a very gentle mission compared to droneship landing missions or even RTLS single-stick missions.It even looks to me like FH side boosters could get rid of the entry burn entirely. After all, they start their entry burn with less speed than normal missions have after their entry burn. The only reason I can see why they might not be able to do this is if they need the steering capability of the burn. Even if so, they should be able to reduce the burn to a burp of just a second or so.
