I remember receiving the same pre-order pricing guarantee on previous purchases for items *not* listed on that page. I followed up with Amazon because as you correctly pointed out, the page certainly makes it seem that the guarantee only applies to the listed items. Here's the reply I received:

-------------------------------
Hello from Amazon.com.

I understand that you've contacted us as you'd like to confirm if pre-order price guarantee is available on electronic goods such as cell phones.

I believe I can explain this for you.

Yes, pre-order price guarantee is available on electronic items.

Whenever you pre-order an item the price we charge when we ship it to you will be the lowest price offered by Amazon.com between the time you placed your order and the release date.

Please note that our Pre-Order Price Guarantee applies only to items sold by Amazon.com, and not to items (or prices) offered by other sellers on our site.

I've included some additional information below. Thanks for shopping at Amazon.com.

*****
WHERE CAN I FIND MORE INFORMATION ABOUT AMAZON'S PRICING POLICIES?
Please visit our Help pages at:

http://www.amazon.com/o/tg/browse/-/468502/

*****

Please let us know if this e-mail resolved your question:

If yes, click here:
http://www.amazon.com/rsvp-y?c=wduuegrg3431604782
If not, click here:
http://www.amazon.com/rsvp-n?c=wduuegrg3431604782

Please note: this e-mail was sent from an address that cannot accept incoming e-mail.

To contact us about an unrelated issue, please visit the Help section of our web site.

Best regards,

Prakash
Amazon.com
We're Building Earth's Most Customer-Centric Company
http://www.amazon.com/your-account
----------------------------------

The main condition to note is that the item has to be sold by Amazon.com, which is the case for the N900. My guess is that when someone wrote the pre-order price guarantee section, they were mentioning various items as *examples* as opposed to stipulating specific items that were covered on the guarantee. Methinks someone needs to go back and do some rewriting.