Not sure if that's the reason, but possibly the page was created because the discovery of the exact image you need to flash on your router is kind of complicated for novice users.
Since the downloads listings are grouped by platform and majority of people have no idea what platform their device belongs to, I believe that page nudges people in the direction they need to follow to find the correct LEDE image for their device.
Ideally tho, the download page should be something like https://twrp.me/Devices/ -- where you can search in page to find your router or just start typing the router model to get relevant links.
Actually no, the more I think about it, the more I like the twrp's page specifically for the purpose of finding the correct download.
The new (current) ToH is a great tool to have, however for the new user struggling to find the proper file to flash on their device twrp's approach is better because:
There's just one field to type in and it auto-filters content without having to press enter.
It displays a simple result which is linked to a page with all instructions/links to relevant files for your device.
It works on mobile very well (LEDE ToH page barely works on mobile and even on my computer t's very slow, you need to scroll a lot). It's debatable if people are going to download LEDE files onto mobile devices, but a lot (to the tune of more than half) browsing is now done on mobile devices, so it's not unreasonable to assume some people will be checking if their device is supported by LEDE from mobile.
@stangri is right - I wrote the "Alternate Directory Search" page in an effort to separate/factor out the "finding your firmware image" discussion from the "Standard Flashing Instructions".
Step #1 of flashing is to find the device page and firmware you want to install.
If you can't find an image, the text on the Standard Flashing Instructions sends you to the Forum, to the alternate search page.
This page might go away when the ToH is completely imported, or could be updated with better info.