I listened to Reiss's (the passenger cited in that story) account on his podcast [0], and it's somewhat ambiguous. There are periods of spotty communication and long periods of the sub just getting lost. But not comms system/transponder abruptly going out and not being heard from again.

David Pogue seems to concur with this [1]. He saw them lose track of where the sub was located (wrt to the Titanic wreck), but he said the support ship never lost the ability to communicate with the sub.

[0] https://bleav.com/shows/what-am-i-doing-here-with-mike-reiss...

[1] https://twitter.com/Pogue/status/1671524465736335366