I have a version of that style, and the 'strum noise' is coming from the Phrase1 and Phrase2 parts. The Phr1 part is using SteelGuitar Megavoice, and Phr2 is using the HiStringGtr Megavoice. The patterns in these parts are only playing high notes above C6, which is where the strum effects are.
All he is doing in the video is playing a chord (which then continues to play) and then turning off style channels. When he turns off all parts except Phr1 and Phr2, you only hear the strum noise effects. There are chromatic guitar parts using a normal voice in Chord 1 and 2, and a megavoice in the Pad part. When these are turned on along with the two Phrase parts, you hear the guitar plus the strum effects.
You can do the same on a PSR.
If you look at the style in MixMaster or a DAW, you will see what is going on in the Phrase parts.
Regards
Ian