Leaving aside how stupid this is, and how much Steve must be regretting doing this, I think there is a bigger concern.
A SNCO writing a letter for personal gain, on headed paper from the unit he serves at?
Whether or not you consider it to be a dreadful attempt to get an upgrade (which it clearly is) there can be no excuse for the abuse of the letterhead.
I hope that he's the exception, rather than a typical example of what passes JATCC nowadays. How has the RAF got to a point where anyone thinks this is acceptable?
What standard of general service knowledge and service writing is currently demanded of candidates?
No matter what the reason, no matter the subject, a Sgt sending letters on headed paper from the School? Strange days indeed.