Yeah, my thoughts above are what it is then exactly!
I run my parking lights in situations when the sun goes down and is beginning to get dark, when this happens I always have my fogs on with my parking lights. So, parking lights are never on by themselves. The mod wouldn't bother me at all and I actually prefer it, BUT it would mean you can never turn your fogs off..ever..wheile your headlights are on since you must have your parking lights on to turn your headlights on!
You could add another relay to eliminate this problem. You could use the griound off the parking light relay and use the signal wire off the headlight relay to activate the fogs. This however would require the headlights to be on in order to use the fogs. Then if thats a problem, there are several other ways around all that. Lots of options just depends on what you would like to do????