pppoe configuration

Thats they way they decided to do it??

Ie. you need something to setup the process that will be doing the "dialout" for the PPP, and while for the earlier PPPoA, they used the interface dialer, they chose not to for PPPoE?

Probably because they worked on the server end first. The VPDN groups can be used for many more than PPPoE, thats where you end up doing L2F, L2TP, PPTP, as well as PPPoE (server side).

When they did the client side, they probably just made it all part of the same, as you would do client-side L2TP through a VPDN group as well. So they did the same for PPPoE within the VPDN group.

I guess it seems straightforward enough to me, but I deal with all the above, not just a client PPPoE setup. As I've said before, the cisco routers are more like a hammer and a bunch of boards, rather than a pre-fab kit. You can do so much more, but you have to put some of the pieces together in new ways, but you aren't constrained by the existing design (so much).