I've no idea where rocketmagnet got the idea a gaint trance has even a vaguely similar suspension design or recomended usage.
The Esommet used a 4 bar horst link design with a decent amount of progressiveness to it's leverage curve while the Anthem uses giants maestro design (basically a D-W link virtual pivot design) which is also mainly progressive in it's leverage curve but the overall ratio is lower (2.1). Meaning lower shock pressures will yeild firmer shock support than the Sommet.
The E sommet is also a long travel Enduro based Ebike built to take regular rough gravity based riding while the Anthem is a short travel non E XC/AM bike built for lightness. The two bikes are not comparable in the slightest.
The frame, fork and stock components, incl wheels/tyres on the esommet are easily upto surviving a 280lb Enduro rider.
The bike is kinda overkill for riding blue and red trails, but will be absolutely fine if that's what you want to ride on it.
as for whether the suspension can be set up correctly a 280lb rider. Yes it can.
The shock of the Esommet has 65mm stroke and the rear end yeilds 160mm travel
This gives an average leverage ratio of 2.46
Max pressure on the super deluxe shock is 325psi and the Lyrik 148psi
You'd probably be looking at running somewhere around 280psi in the shock and 110-120 in the fork
You didn't mention whether you were looking at the Fox or RS builds so I've only given aprox pressures for RS
[Ooops. hadn't seen Billy's post above, basically we're agreeing though)