Why would a trailing slash make a difference in this URL?
The technical answer or is this a request?
The technical answer, in one step removed technical lanuage (since file/directory isn’t a URI thing):
The first is a directory. Web servers and content engines almost always have defaulting rules when you ask for a directory, just like http://mcneel.com/
The second is a file with no extension: usually, there are no general rules for this except to 404 but in this case it would be tempting to create an Alias or the equivalent in whatever content engine they use.
I think an URL should behave the same with and without a trailing slash, it is the endpoint that counts. As a user this is very confusing, like when I was copying and pasting this URL and suddenly and unexpectedly it gave a 404.
And the request is to look into this and maybe fix it.
I’d vote for that in cases like this: popular links near the top level. Or at least a “Did you mean?” prompt on the 404 page.
In the general case, it may or may not be easy to be entirely consistent and you’re stepping into a fight between a few different hornets’ nests.
url trailing slash endpoint - Google Search