I'm am a DSA Assessor also.
More and more students are attending assessments saying they want a Mac, but rarely do we agree to such requests unless there is a specific 'need' to back it up. Some of the funding bodies, Student Finance England being the main one, have issued guidance as to why such recommendations are rejected, cost being the main implication. For most dyslexic students we are trying to meet needs such as difficulties with writing and reading, so even they are on a Mac based graphics course it doesn't mean a Mac is needed to write an essay or read text.
Unless student is on a course which requires Mac specific software, or has solely used a Mac for some time, one would not be recommended.
We have students with Macs who need hours of training to get them to use a Mac as they say the need one for their course and haven't a clue how to use them. This a waste of our time and tax payers money.