Well ecl.. It may not be mandatory, but it does make it a hell of a lot easier. Because otherwise you have to jack the car up as far as possible, so that the spring is fully extended.
And also the bottom mount point is very tensioned (unless you reduce the spring) meaning you can take off the nut, but it's going to be very hard to slide the strut off... p.s. you will probably need a breaker bar on the bottom nut as it's pretty solid (19mm).
Also, if you don't take out as much tension as possible in the spring, and you do manage to pop it out, it's likely to shoot somewhere bad, and destroy something.
Anyhow, it might be possible without, if the car is jacked very high.. but for $50 for spring compressors, worth getting
Ok.. compliance work is done (I hope).. engineered hopefully end of this week / start of next.. on road, middle of next week