SHDN pin and LTC4020

I'm trying to design a SLA battery charger with the LTC4020, and I'm not clear as to what the SHDN pin does.

According to the datasheet:

SHDN (Pin 9): Precision Threshold Shutdown Pin. Enable
threshold is 1.225V (rising), with 100mV of input
hysteresis. When in shutdown, all charging functions are
disabled and input supply current is reduced to 27.5μA.
Typical SHDN pin input bias current is 10nA

The language suggests that the SHDN pin trips as the voltage on it rises from below 1.225V to above 1.225V, but this makes no sense: why would you disable charging when the voltage is going up (unless it's for an over-voltage condition, which the LTC4020 is specifically designed to avoid doing in the first place)?

Does this description actually mean that the LTC4020 enables charging when the SHDN pin crosses the threshold from below 1.225V to above it? I think this is how the part actually operates, but that means that SHDN is either misleadingly named or is an active low-signal that isn't marked as such.

Please elaborate on how the SHDN pin is meant to function.