This fixture is a Multi-Tap fixture, I never knew AE made their small 250 watts multi-tap. The GE ones were oly single-tap. But the cooper ones are Multi-tap though.
GE makes multi-tap small fixtures. They'd loose business to AEL and Cooper if they didn't. I know they don't offer 4-bolt fitters at all for the small fixtures though and the M-400R2-A2 aren't in 2-bolt as far as i know.
I guess it's what they thought was a better design?