If it is really low FOV it will not snap for spectators or OW demos. Pretty sure Sen merged pSilent and Silent into one option a while back. You can test your settings if it's snapping by recording a POV demo in aim_botz, use the command "record test" to start a recording, shot some noob bots, use the command "stop" to end the recording and then use the command "play test" to view it back.
When testing, it's good practice to shot a variety of enemies from multiple distances especially when FOV selection mode is set to 3D, and turn off silent aim before reviewing the demo. Also, don't use RCS with silent aim, with satan5' RCS it can cause problems sometimes.