An iPod Notes Developer PDF is receiving attention for referencing a "touch-screen" iPod with the following passage:
Note: Linking to photos and videos [from Notes] is supported only for 5th generation iPods running iPod Software version 1.2 or later. All other Notes feature capabilities described in this document are supported for iPod models with display screens, beginning with the touch-screen models.
In context, the reference appears to refer to older iPods and may simply be a typographical error, instead intended to refer to "touch-wheel" models.
"Touch-wheel" iPods were introduced shortly after the original iPod introduction ("scroll wheel").
Update: The PDF has been corrected by Apple to state "touch wheel".