TeeCee, the 441 number comes from the Eric Stasik report entitled "Royalty Rates And Licensing Strategies For Essential Patents On LTE (4G) Telecommunication Standards".
He lists a table with ETSI declarations as of Sept. 2010 that includes:
InterDigital Technology Corp 282
InterDigital Patent Holdings 155
IPR Licensing, Inc. 4
Which total 441.
As of today, there should be a lot more than 441 declarations by the company. I'm not sure how to interpret the numbers used in the new report (Article One Partners). Perhaps, as you suggested, they are omitting patent declarations submitted by IDCC's "other" moniker(s). Maybe they applied some sort of filter to not include those patents that apply primarily in other technologies (like UMTS). Or maybe they just didn't care if the info was accurate or not.