You should genererally stay with what is factory recommended in most cases, although that can be tweaked a bit.
JMHO, but I don't think you will have a problem with these plugs. The double ground electrode plugs were used with Toyota's ignition system at the time (forget the technical name), but it is called a "wasted spark system".
Most plugs fire at the top of the compression stroke, but on this system it also fires at the top of the exhaust stroke.
In theory, since the plugs are firing more often the electrodes won't last as long. It's not something I think you should worry about.
If you have any concerns pop the plugs back out in a couple of weeks and examine the tips. If they're light tan in color then that means normal.
The wasted spark system is nothing new; Harley Davidson has been using it on their motorcycles since way back in the 1920s.
Harley Davidson has only used single electrode plugs all this time with no problem.
Even some motor home power generators such as Onan use the wasted spark; with single electrode plugs of course.