Nothing to do with linked brakes. My CBR600RR and VFR1200 both had linked (combined) brakes and neither had that tendency.
No idea about Goldwings, but some bikes are indeed prone to standing up in a corner under breaking. That was an early complaint on Buell XBs with the ZTL brakes for example. It was a repeated theme in early track reviews. I have felt in on other bikes to one degree or another.
If your bike does it and you know to expect it, it's something you get used to and a non-issue, IMO.
However, it more likely there's a technique issue at play. Like when the brakes are applied, or body position, or not realizing that he is changing the steering input during braking with his weight shifting forward.