On the videos you just posted, in both of the other places where Jermaine sings it correctly, he also sings the correct following line, "Although a tear may be ever so near," and not, "all through the years we'll be ever so near." There must be a reason or he wouldn't change it. IMO
Are these slip-ups or deliberate? I think you're right in speculating it's Jermaine 'cleaning up' his Smile performance. It may be connected to his tweet about 'MJ is dead' and hoaxers should stop. MJ is making it hard for us, but we should never give up!