Orlite "fixed" this problem in later designs, so I don't think you can blame Bushmaster.
Certain lot numbers of late model Orlites DO fit in Bushies.
It has to do with the bevel on the inside of the mag well. Given that Bushmasters are pretty good in the mil-spec areana, I'm guessing it was Orlite's problem. Can't say for sure, but since their later mags do work........you figure it out.
I like Thermolds better anyway. Every Orlite I've seen has been worn and was showing the metal mesh. Granted, I haven't owned Orlites, so I'm not an expert on them.
From the MAGAZINE FAQ:
Orlite magazines were developed for the Israeli Armed Forces. The bodies are made from high-melt-temp black nylon with a steel reinforement mesh imbedded in the top 1.5 inches to strengthen the feed lips. New Orlites come with a rubber cap to help keep sand out of the mag.
Orlites have a rib around the middle of the mag which helps to seal the bottom of the mag well and also prevents the magazine from being over-inserted and the feed lips damaged. The location of the rib was based on the deep mag well beveling on Colt M16s, and in ARs that aren't beveled as deeply, early Orlites won't seat completely. This is easily correctable by trimming a bit of material from the top surface of the over-insertion rib; just enough to allow the mag to seat. This problem only occurs with early Orlites with mold numbers from 0/1 to 0/19. Starting with batch 0/20, the rib was moved about 1/32" further down the mag body, and these later mags work in all ARs with no modification. Used Orlites are often found at gun shows with their over-insertion ribs completely ground off. Avoid these mags, as it's too easy for these mags to be over-inserted, banging the feedlips against the bolt or getting stuck.
Orlites are quite reliable, and were general issue in the Israeli Army through the 80s, but it was found that they don't hold up to hard combat use as well as USGI mags, which Israel switched to in the 90s.