One thing I'm noticing lately is that Wengers are generally more expensive than Victorinox. I think Victorinox is aggressive with their pricing to try to discourage competition from China. It has worked so far, but that may have also been what drove Wenger into dire straits.
The lock does protrude. It would indeed be in the way for certain types of cutting, especially a lot of the cuts in whittling. But this knife is a poor choice for whittling anyway, because a) it hasn't got a small blade, and b) the large blade it does have, has a lot of belly. For day-to-day odd jobs, the lock is never in the way.
If I grab the knife in a death grip AND bang the back of the blade on something, I'm sure I could get it to release the lock. But the highest point of the lock release button is placed so it goes between the index and middle fingers, so it would really have to be a death grip.
I'd say the fact that it obscures the nail nick for the scissors is more of a drawback than any concerns about inadvertent lock releasing.
As for whether the lock is "needed" or not is akin to whether I need guard and splitter on my table saw. It's a safety feature, and if that safety feature impedes normal operation of the device, the user will reject it. So the key is designing it so that it doesn't get in the way too much. (if at all) Furthermore, the guard and splitter would only be needed if my technique was wrong. But in case that happens, it would sure be nice to not have a chunk of plywood flying at me at 130 mph. (or to not slice the back of my finger open, in the case of the non-locking pocket knife)