He uploaded loe and all evidences along with application
He raised cse to upload the pcc which he received after submitting his application waiting till the last date
Yes he could appeal which is tedious and the decision might not always be in applicants favour. So he rather preferred to come back to the pool and resubmit with all docs as it was easier and quicker
If he did exactly as he was told, there would have been no problem for him to appeal. I have seen somebody whos application was cancelled wrongly and their application was reopened (they did not accept her medical, also it was done in a correct way). There is nothing tedious to appeal if you have strong evidence, that you did everything correctly.
I also know one different case on this forum, where applicant has uploaded PDF coded in some different way and if you have used one software you would only see the first page. But that one has appealed as well.
I have also read about the case where application was cancelled without any reason at all (looked like a typo mistake on their side). It was reopened within 1 week.
Nobody can give you a guarantee, that they will not do a mistake in your file and cancel it (human factor will be always present).