I use an automotive SBC L99PM72 from ST and in the datasheet i found the term High Z Grounded (see attached picture)
Anyone any idea about what that means ?
my guess would be the literal "high impedance connection to ground". eg, if you had a capacitor on the load, the source would discharge it to 0V, but would do so slowly due to the high output impedance. Whatever this is probably is unbiased at these low voltages and can't force the output to anything. Some additional circuit exists to weakly attempt to force the output to 0V.
What it means here is that the output state is low, but
has a very weak drive (consequence of Vdd <= VT(N))
and probably should not be relied upon for strength or
speed.
Looks like a undervoltage lockout / power on reset type
function, where it's always a challenge to get truly
monotonic response at the voltage-starved end of things.