That is true for the FM2, FM2n, FE2, FA, and FM3a. Not true for the FM and the FE.
A link showing a pic of an FM body with the button plainly in sight is here: http://www.flickr.com/photos/marcus20/3618725672/
APUG: F3P, F2AS, Nikomat FT2
Nikkors: 18-70/3.5-4.5G AF-S DX (f/D2x), 20/3.5 UD, 24/2 AI, 35/2 O, 50/2 H, 50/1.4 S, 85/1.8 K, 105/4 Micro AIS, 180/2.8 PC
'tax gear: Spot II, 55/1.8 Super-Multi-Coated Takumar
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