These were basically home assignments that we would demo at a lab for a grade. The lab machines had several "resident" programs running on them (some legit, like basic AV, and some installed by lab admins for their own questionable purposes), so the amount of available RAM varied wildly, sometime dipping as low as 300KB. The TAs knew that, but didn't care enough to do anything about it.
So when an assignment that you did on your own machine failed with "oom" at the lab, it was plausible that it was due to all the junk taking up too much space on the lab boxes. The assignments themselves were math-heavy physics modelling tasks, so you they did actually need a lot of memory.
All that said, I think only once someone used this "trick" to get an extension and it was because his truly needed few more hours to hammer its sim into converging.
If it didn't cleanly compile and run on linux, it was a autofail. I found a discrepancy in MPICH2 the hard way: it would correctly implement my leader election on my mac, and on my little raspberry pi, but not on a Solaris linux!
Once, I implemented an interpreter/compiler for a toy-language in Opal (a functional language developed and maintained by my prof). A compiler for Opal was only available for Linux. I had zero experience with Linux and no intention to gain any. So I wrote my code without compliling/testing. Suprisingly, I got a good grade with a remark that the grade would have been even better without syntax errors :D
