Well that's an interesting way to make backlit keycaps.
It's patented too which is why they aren't seen on any keyboards other than TG3s (Deck). However the edge between the two shots seems visible on every keycap (I haven't use one personally so I wouldn't know if that is noticeable).
Oh, it's noticeable all right.

I just got my first TG3 today, from the pictures it almost looked like the keycaps had labels on each one. Up close you can see the line between the two cap materials, but there's no apparent raised seam. The inner portion of each keycap is a different texture, but they feel great, kind of like a less "gritty" PBT.