Copter can still arm without GPS lock

My quad is running Pixhawk , MP 1.3.50, arducopter 3.5.2.

In the MP config page, the parameter ARMING_CHECK is already set to 1, meaning check all including GPS lock.
I tried to arm the quad as soon as I power it up, without GPS lock (as viewed from the MP HUD), but time and time again, the motors can be armed.

What has gone wrong ? Apprceiate any help.

Check your flight mode,see this.
Stabilize,Alt Hold,Acro,Sport,Land don’t need GPS lock.

Yes, cannot arm in GPS modes if no GPS lock. I requested changes here months ago: including

a tone to indicate 100% ready to go, GPS 3D lock obtained?
a "can't takeoff without GPS 3D lock" parameter?

If the circular or polygon fence is enabled it will also require a good GPS position to arm.