Yeah, removing the top of the strut from the bottom of the tilt mechanism. This is the video guide...Is that the gas strut? They are an utter pain to remove. WD40 and a hammer is probably the best approach on the tight end (hammering from the inside, you need to unscrew it from the chair base). The other (bump stop) end can usually be removed by popping the spring.
I'm assuming the one they used to demo the procedure in the video was brand new and didn't have hundreds of hours of "being sat on" to force the parts together.