There's some misinformation here. First, that fork isn't aluminum, but steel. Aluminum forks still exist here and there, but they were never common and they're a lot more uncommon now than they were 20 years ago.
A front hub motor has little perceptible effect on steering. It's not like you can wheelie a longtail bike anyway, so it's unlikely you'll notice a difference one way or the other.
However, a hub motor wheel is weaker, like for like, than a normal bicycle wheel. So you might as well use it in the front of a longtail, where the rear wheel can occasionally be called upon to carry really heavy loads, e.g. an adult passenger.
Longtails distribute a higher minimum amount of weight to the front wheel, so traction/wheelslip of a front hub motor won't be an issue like it can be with a regular bike.