Will a 73 inch long electric bike fit with 28 inch wheels
You can find the specification sheet for the racks here:

https://www.sportworks.com/assets/files/Model-Overview.pdf

The maximum wheelbase (distance between front and rear dropouts) supported is 44" or 48" depending on which model is installed.  A bike that's 73" end to end probably has a 45-46" wheel base so you may not be compatible with all racks.

Note a beefy e-bike with battery installed could also easily exceed the 55lbs rated weight limit.