Those aren't valid Euler angles so what you get would be pure guesswork.
X angle is pitch and you would expect +90 to be looking straight up and -90 straight down.
Y is yaw which you would expect to be -180 to +180
Z is roll so you would expect 180 to +180
Through experimentation I found that the gimbal lock positions in GG are on Y rotation!
i.e. the limits are actually:
X -180 to +180
Y -90 to +90
Z -180 to +180
(when I say 90 or 180 of course I mean 89.99999 and 179.99999
)
Euler angles are so damn difficult to work with I created a quaternion library before I pulled all my hair out btw.
Been there, done that, got all the T-Shirts!