They changed this because it turns out that the same phenomenon that leads to private pilots taking undue risks in the rest of flight ("Get-there-itis") also makes them reluctant to pull the chute even when it's clearly their best option. Pilots who clearly couldn't reach a safe landing spot, yet had working CAPS would dig themselves (and their passengers) a grave rather than just pull the handle. So teaching them to start by assuming they'll pull the chute and only then considering whether there are other options reduces the fatality rate.
> Four CAPS deployments occurred successfully at higher speeds, 168, 171, 187 and 190 knots indicated airspeed, and one deployment failed at an airspeed estimated at over 300 knots airspeed.
* https://www.cirruspilots.org/Safety/What-Is-CAPS
Anything lower than that will forward-motion stop the aircraft. AFAICT, there is a need for 2000' (650m) of altitude above the ground for the system to deploy in time to be useful (slow descent).