Since GRR opened at DCA in 2001, it has had a
summer mode and a
winter mode.
Although it really depends on what mode the ride is set on when it opens for testing in the morning... and by what specific mode each operations manager chose that day... regardless of the season.
Just like the wave machine near California Screamin'.
If it's not broken and it's not operating... it was by particular choice of that operations manager, that day.
In winter mode... the timing of geyser near the end of GRR is changed so it doesn't get the rafts wet, the hydrolators
(rapids blowers) are turned down a bit so the river is a bit slower and the water level is indeed a bit lower than the summer months operations.
Also... the leaky pipes on the lifthill are also usually turned off during winter mode.
Being this is October and Anaheim is still quite warm most days...

GRR is probably still operating in summer mode some days.
The spinning drop doesn't spin the raft when it's malfunctioning.
It's not turned off during winter mode.
It was installed to be part of the intended ride experience all year long...
GRR also doesn't have any actual on-ride waterfalls to turn off or turn down... as none of the waterfalls on GRR actually get you wet.
At no point of GRR did the Imagineers use the
same lame trick nearly every other rapids ride uses by making the entire raft get wet by going directly under waterfalls.