OK....I may have found my answer. Probably the 'telephony' referred to as not working with this modem would be if you have VOIP service through the cable provider. The cable provider gives you a different modem if you use their VOIP service....I do NOT use the cable VOIP service, I use VoicePulse so I think this modem will be fine as the VoicePulse module just connects to my router. Probably something like Vonage is similar.
I use this modem with VOIP. You can not plug a telephone directly into the modem - you must have other equipment to do that. In my case, I have an Ooma Telo that plugs into my Internet connection, and the phones plug into it.
Thank you. Your diligence is commendable. This topic is not relevant to my interests, but I applaud your thoughtfulness in posting the results of your search so others may benefit from your efforts. Again, thank you.