No. Not even close.
I don’t know which is faster. But I know the Fronius is very fast.
Fimer SPA 
Depends on PV-inverter. With Fronius, after two minutes of no comms, it goes back to full power. If I read sunspec correctly, this is what it is supposed to do:
Each of the immediate control functions, except connect/disconnect, has an
associated enable (Ena) register. Each time a control value is changed, the
associated enable register must be written with the ENABLED value (1). If a
reversion timer is set for a given control, the associated enable register
must be cleared by the device when the timer expires.
Some of the internal solutions by manufacturers, eg a Fronius with its own smart meter or an SMA with a home manager, will stop making power if it loses contact with its own meter.
Edit: The two minutes isn’t Fronius specific. The protocol allows you to set the timeout. Every time you write to the PV-inverter, you tell it 1) this is the power limit, 2) it is valid for 120 seconds, 3) the limiter is ON. According to that blurb I quoted above, you must set the limiter ON every time you write a limit. That means you write 3 16-bit values every time, the limit, the timeout, and the enable flag. Well technically you write 5 values… there is also a ramp rate and a time window… but these are optional. A PV-inverter doesn’t have to support them. It need only support the limit and enable fields… if it supports model 123 at all.