Chris has played fretless on a number of things over the years. Listen to parts of Tales From Topographic Oceans, for one.
Heh.
I would think that you of all people would know that when someone posts on this board about a classic Rick tone, they're not talking about fretless figures in Tales.
Yes, Squire played fretless. He also played 8 string, 5 String, Fenders, and that wierd ass green thing he used for 92015 that I can't remember the brand name of. He also used multiple effects, tunings, overdubs, and his sound is different on every album. And he quite often dressed funny. Have we covered it?
But he's not famous for any of those things. The OP was asking about his classic Rick tone. Cuz that's all anyone asks about. If the OP plays fretless figures from Tales, the audience will think, "hey that's great, now can you do Chris Squire?"
OP: you still can't approximate Squire's classic sound playing fretless and flats no matter how many Squire fans go "er, on this one particular figure on this one particular song on this half baked album Chris tripped over a flanger, fell flat on his ass and while doing it glanced at a fretless 24 string, so that's how he gets his sound." No. You need a fretted 4001/3, a pick, roundwounds, a little overdrive, and a little punch in the high frequencies. You can't get that from a fretless Wal strung with flats. You can still play like him, but you can't get that sound.
Derailing: When I got my first fretless, I worked on my chops by trying to play anything on my fretless that I could play on my fretted. I used Siberian Khatru and Heart of the Sunrise as my models. Great for learning to get around on an unmarked fretboard but it was obvious that that ain't the sound.
And I'd rather listen to Talk than listen to Tales ever again. Really.