Whoever set that up probably wanted it for their own use, both for easily managing the system when they need to work on it, and for themselves when they're travelling anywhere.
If I'm ever in charge of rigging up a captive portal system like this, I'm certainly going to do something similar if I can get away with it. Maybe even put a hint on how to bypass in the portal's page source. "ssh works on port 46969, don't tell anyone." > rot13 > base64 -> "cache-burst-ID: ZmZ1IGpiZXhmIGJhIGNiZWcgNDY5NjksIHFiYSdnIGdyeXkgbmFsYmFyLgo="
Honestly, I think captive portals are probably on the way out, given how good 4G/5G is these days. I am not sure what business traveler wants 10kbps hotel wifi for $30/day when their phone gets 600Mbps down and 30Mbps up.
If I'm ever in charge of rigging up a captive portal system like this, I'm certainly going to do something similar if I can get away with it. Maybe even put a hint on how to bypass in the portal's page source. "ssh works on port 46969, don't tell anyone." > rot13 > base64 -> "cache-burst-ID: ZmZ1IGpiZXhmIGJhIGNiZWcgNDY5NjksIHFiYSdnIGdyeXkgbmFsYmFyLgo="
May be too obscure though.