Yep, that's the only pre-order incentive that makes sense, especially for digital pre-orders.
Yes, this is actually a good idea and sadly thats what was largley ignored by SE at the end of this.
Honestly I don't think a tiered system for preorders is a bad thing if its done RIGHT, the BS that SE tried to pull with this was stupid but it could work if publishers were willing to actually make the bonuses feel like an actual reward and if they disclosed the numbers for each tier and updated it either daily or weekly on where the numbers were currently at.
If for example take Deus Ex had done something like the following...
Tier 1 (250k Preorders): digital artbook and digital soundtrack included
Tier 2 (500k Preorders): Physical soundtrack and artbook, extra disk with making of videos (basically what you'd normally find in an 80$ CE)
Tier 3 (1 Mil preorders): Game releases 1 week early (4 days is stupid)
Tier 4 (4 million preorders): All DLC at launch and in the future is free to everyone.
Now something like that could get behind.