Here is a real picture of it.
And the picture of the toy is 3 months old.
Here it is:
http://www.starwars.com/collecting/news/2002/01/img/hasbrosabers_bg.jpg
You get a great reach, freedom of movement and fine control of your sword.
What you wouldn't get is a super-powerful blow. So what? One quick stab and you'll kill your opponent.
Fencing is a sword art from a time where opponents wear no armour (because of early guns). The important thing was to be fast and accurate. With an armourless opponent what you wanted as a long, quick blade, no need for it to be heavy at all.
Kendo, the dominant inspiration for earlier fights, was about fighting people in exquisite armour that was very useful in pre-gunpowder days. You needed strong, poweful blows to beat your opponents guard aside and slice through his armour.
As armour doesn't STOP sabres, the fencing form is more sensible to use.
Trouble is it normally looks damn dull. Obi-Wan and Vader fought with a two-handed fencing style in ANH, and that was actually pretty good but they couldn't do it more than once.
Nick Gillard, though, is a genius. Also, it is only Lee fighting this way, which looks good against a more flashy opponent. And in any case Lee would appear to be changing styles all the time anyway, like a true Master (but a right show-off...)