I'm not really sure what you're saying, or what the criticism is, if it is one - but shortly before the bit you quoted OP links the code on GitHub: https://github.com/WebSheets;
And you can't really conclude they made a poor implementation choice on a report of completing it successfully (albeit too successfully even, too much of Excel implemented, and then fixed by removing that (how do you do that to your XLS download link?)) on time within a short deadline.
The takeaway is supposed to be 'don't get too attached to your code', which in some circumstances (not this one) might mean 'don't succumb to NIH syndrome, use an XLS download link', but that's not the whole.
And you can't really conclude they made a poor implementation choice on a report of completing it successfully (albeit too successfully even, too much of Excel implemented, and then fixed by removing that (how do you do that to your XLS download link?)) on time within a short deadline.
The takeaway is supposed to be 'don't get too attached to your code', which in some circumstances (not this one) might mean 'don't succumb to NIH syndrome, use an XLS download link', but that's not the whole.