No, the mohawk does not indicate that the hog is Russian. It is not a diagnostic trait of being part of the "Russian boars."
Phenotypic expressions (e.g., visually identifiable traits) of genotypes (in this case, "Russian" hogs) is not reliable in hogs except in very limited circumstances.
Part of this problem is that the domestic hogs from which our ferals are primarily derived are domesticated from "Russian" boars (more aptly called Eurasian hogs). These are the same species - feral, domestic, and Eurasian. There are distinctions at the subspecies level.
Identifying Eurasian hogs based on phenotypic traits cannot be done on a singular trait, such as the mohawk, but must be done using a variety of traits, such as specifically a whole series of craniometric measurements.
Things like the mohawk, thick hair, split hair, straight tail, etc. simply are not diagnostic and can be found in domestic hogs of some varieties, feral hogs, or Eurasian.
To listen to everyone's stories from all over the country, there are countless tales of all the "Russians" brought in and either turned loose or that got away. No doubt there have been plenty. No doubt their genetic contributions have been widely spread across the population. You could pretty well argue that any 2nd or 3rd generation feral hog likely has some "Russian" in it. Of course, you could argue that your Berkshire domesticated hog does as well since most domesticated hogs are derived from Eurasian stock. The question is then really one of how long ago it was.
A lot of people worry about the "Russians" being more aggressive. Maybe they are, but you probably have some "Russian" in you as well based on genetic admixture of the population. Do you feel aggressive? I make this point as a joke, and for good reason. Generally speaking having some genetic variation in your background isn't likely to casue you to have significantly different behavior than your peers in the rest of the population. People will often attribute aggressiveness in a hog to being "Russian," but if "non-Russian" domestic pigs get upset and kill humans every year or so, injuring a lot more. There is plenty of aggression in the pig population without the need for attributing it to being some mythical superpig blood line as done on the "documentary" called "Pig Bomb." Any feral/wild animal is potentially dangerous, but by and large, dangerous pigs are the one that you are activily trying to hunt, are cornered, wounded, or you are trying to handle them (such as after catching them with chase dogs). In these circumstances, the "aggressive" hogs are only defending themselves. Outside of those circumstances, "attacks" by hogs are virtually non-existent in the wild.
"If you look through your scope and see your shoe, aim higher."
-- said to me by my 11 year old daughter before going out for hogs 8/13/2011