The article kind of addresses this. Texas really does have more frontage roads than other US states. In the specific example cited in the article's headline photo, both the US 75 and I-635 have frontage roads that cross each other. They stay at ground level whereas the highways elevate. Part of the reason this specific interchange has so many levels, though, which is not addressed for some reason, is that both highways have high-occupancy express lanes that are separated from other traffic and have separate interchanges with the other highway as well as separate on-ramps and off-ramps to the frontage roads. This one is particularly bad because it's where the express lane for the US 75 starts and stops. Normally, the express lanes don't have their own dedicated exits and you have to first exit to the normal highway, but US 75 has an express lane north of I-635 but not south, so there are separate entrances and exits for it here.

Thankfully, I've worked from home for years now, but back in the day, this used to feature heavily in my daily commute. My wife and I worked at the same place, so typically used the US 75 express lane where it existed, and it was a bitch. To go south, you have to get off the highway onto the frontage road and then back onto the highway.