Huh, this idea is new to me. Could you help out with a link? I only found two articles that talk about icebergs and gravity, one from NASA that only mentions taking measurements with a gravimeter [0] and a popsci article from 2011 [1] that mentions the geoid and irregular gravitational field of earth, but only sourced its “sister site” which appears defunct and simply redirected to its own front page, which looks like a garbage fire of pseudoscientific advertisement. I also found a BI article (to which I link with great trepidation) that mentions I think the same iceberg as the NASA article but mentions it is not expected to contribute to sea level rise in any significant way [2].

[0] https://earthobservatory.nasa.gov/blogs/fromthefield/2017/11... [1] https://www.livescience.com/amp/15605-melting-glaciers-alter... [2] https://www.businessinsider.com/antarctica-larsen-c-iceberg-...