Actually it confirms they've opened and checked aspects of your application.
Given many people here have gotten their application back because they forgot to include photos, or didn't check a box, or forgot to sign a page, etc... there is clear proof they do actually at least SCAN the paperwork.
Now, do they check all the details of physical days? Probably not. Do they check the calculator at least says > 1095 days? Probably yes.
So as to the OPs question ... what do you mean by check
I assume you mean sit down in detail, that's later on. And they sit down with you and compare to passport at the Test (even if you don't need a test you still have a documents / paperwork check) and I believe they confirm you can at least speak in English (not sure what happens if you are 80 and don't speak a word)...
If you didn't use the calculator for some reason, I have no idea.
But yes, it's very inefficient. Welcome to the government, any government in fact