Here's how I see it......................
Ms. Maddie Reese is standing in the center of the doorway, on the very first step up. Right behind her is the center rail:
This allows us to reconstruct the width of the doorway as seen in Bell:
Mr. Bell was in sun for 'Bell 1' (= filming Houston St., lower image below), but moved west a little to get a better view on Elm, and so was in shade for 'Bell 2':
Here's about where he is (though perhaps I've put him a little too far east) for Bell 2 (dark gray lines), which is the sequence that shows the doorway. (I am also including Ms. Tina Towner's LOS to doorway, also in dark gray. Please disregard----for now----the light gray line!)
This explains nicely what Bell is showing:
-------------Ms. Reese is on the first step up in center of doorway
-------------Ms. Ruth Dean is showing up in blue behind her
-------------Mr. Lovelady is returning to normal stance after craning his neck (we got a glimpse of that in Towner)
Establishing POV for Bell as well as for Towner, and identifying Mr. Lovelady's craning of the neck in Towner, also explains nicely how these could be simultaneous sequences. Use the blue of Ms. Ruth Dean as your common point of reference:
If Mr. Bell had filmed the entrance head-on, with its centre rail directly in front of him (see light gray line on map above)---------------
----------------then he would be showing more of Mr. Lovelady than Towner's POV allows----though not as much as the glorious full-width shot his own 11/22/63 POV gives us!
And he would be clearly showing Messrs. Roy Edward Lewis and Lee Harvey Oswald over west, as already seen in Hughes and again in Towner:
