The HP Officejet 8610 and the 8615 are the exact same printer, the 8615 is a sub model of the 8610 series and its specifications are the same
I can notice the Compare issue you refer to, I will forware this information.
Generally, the 8620 adds ADF Duplexing (copying, scanning or faxing of a 2-sided original) and a larger touch screen (4.3" inches comparing a 2.65” inches screen of the 8610), those are the 2 differences between the models.
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