Yeah I thought the same thing. As far as I know, EBs were only available as 250 and 350 vans, and I think those came with the 5.4l engine minimum.
Also, interestingly, my E250 RB has a GVRW of 7900, while my E250 EB has a GVRW of around 8500 pounds (from memory).
The 250’s (even extended) come standard with the 4.6l. The 5.4 was an optional upgrade. The 350 comes standard with the 5.4l. So you won’t see any 350 eb’s with a 4.6 but there are many (too many) 250 eb’s with the 4.6l.