There is no such thing as a 180 days visa exemption time limit. I was in Thailand for 3000 days on mostly visa exempt before getting into trouble getting in :)
It's the wording. You can trust Thai Visa Centre. It's their job to know such things since they offer fast track and other services. It can be 1h before your flight if you want to. It's a TM6 equivalent, automated in their online system.
For the NPC commenting: Current cost with agent is about 6k baht to get in if it's from a denial entry, or 4k baht if you don't have a recent denial entry. Multiple agents offer such services including the agency owning this FB group (name on banner above). It's profitable to reject entry so that most will use agent to get in. You can also get in at border with agent. Agents work with different immigration officers. The officer wait for you at the gate and he's/she's the one stamping your passport, that's why it's guaranteed entry.
I used SR Services on LINE app last December to get in at BKK airport. Was 6k baht because I got denied entry in Nong Khai. Thai Visa Center also do it. They are the owner of this FB group (their name is on the banner at the top of the page).
Current cost with agent is about 6k baht to get in if it's from a denial entry, or 4k baht if you don't have a recent denial entry. Ignore all comments about you not getting in, they are NPC and don't understand that they want people to use agent as much as possible, as it's financially good for immigration officer too.