It depends on which 4-track.
You can't do tape saturation, real-time, with a Portastudio as the saturation throughput medium, [efx-box], due to it's 2-head design. If you want to record directly to tape that way, then it's okay, but you can't read back that tape signal in real time, on any 2-head deck.
If you have a 3-head deck, cassette or open reel recorder, then this tape saturation technique is feasible, but you will have a delay in the line to deal with.
The comment about other users touting how they used a [4-tracker/Portastudio?] to get real time guitar distortion has me thinking they were simply overdriving the mixer channels really hard, more than they were using "tape compression". That is, unless they were talking about getting that sound directly to tape, and not talking about using it as a tape compression throughput-efx unit.
I can't tell from the outset which 4-track you're referring to, which makes a difference in the answer, but hopefully that covers it.
Anyway, whatever you're trying to achieve, it couldn't hurt to try. I may not be understanding your question or details.