I use simplified mainly with some DJ mixed in, but was interested in the older systems and while looking up the old manuals I noticed the first edition 1888 did not even mention the reversed vowels (a and e) as an option. In the 2nd and 3rd editions it was briefly mentioned only as an option. It wasn't until the 1902 manual 4th edition that it seems to be mandated as part of the system.
Simplified did away with it entirely. I can see some situations where the ending -rt would be slower than the reverse vowels. Sometimes when you write the r sound you feel like you're putting on the brakes to get the t connected to the r. But I guess getting rid of the reverse vowel system got the go- ahead from Gregg himself, since he was still alive when Simplified was being created in the 1940s.
One other thing, I never did like the j-nt blend in Simplified (also in older systems). This is one situation where I think DJ did a service because it omitted this blend. It always seemed confusing to me to have the same blend for p-nt and j-nt, etc.