Ah! Politics.
Managers need to look good to their own managers.
When asking for an "essay" (report?) he expects a report that will make him look good. Especially a report with an award attached because this sounds like oe of those management wheezes designed to make your manager look like he is a fast track material and here you are pointing out "weaknesses".
If you discover failings then talk to him before committing it to writing .... these things assume huge importance in legal cases..... of course, if there is a serious safety issue then it should be brought to managements attention in the proper manner, give your boss a way to present it or resolve the issue in a manner that doesn't make him look like a goof.
More over, I have done some out standing jobs which my supervisor can't do.
I hope you didn't point this out to your supervisor?
Managers are human too (a sub species, maybe, but human none the less) and they don't ever like their subordinates to be, or appear to be, better than they are. They feel threatened and will pursuade themselves that the subordinate is looking for an excuse to embarrass them and take their job..... your report may well be just that....way to go!
The one thing worse than to speak inadvisedly is to write inadvisedly. One can always tamper with peoples recollections of what was actually said or the tone in which they were spoken but the written record?
The Moving Finger writes; and, having writ,
Moves on: nor all your Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all your Tears wash out a Word of it
-- Omar Khayyam ... how wise that man was.
The lesson best learned as early in your career as possible is that the workplace is a complex environment which is not ruled by logic but by human weakness and politics. Diplomacy is your best survival tool, that and an up to date CV.
JMW