Wifi channel 9 with 40mhz Upper Extension

Honestly, do not know the answer, but is it considered a grey zone to have channel 9 selected but use upper 40mhz extension which goes into 12,13?

It would be hard to detect because the channel 9 would be the advertised channel, and 40mhz will only be assumed to be lower extension. Only a tool which shows detailed info like wifi analyzer might detect me using 12,13