The quote does make it seem a more likely prospect than it actually was. The Bee Gees offered the song to ABBA, to be recorded for the Saturday Night Fever album, but ABBA simply wasn't interested because they would never use outside writers.
In the end, of course, it was given to Yvonne Elliman instead, who coincidentally played the same part as Agnetha in Jesus Christ Superstar.
It would have been a bit brilliant to hear an ABBA If I Can't Have You. I'm mainly an Agnetha fan, but I think that technically this song would have worked best as a Frida lead, with Agnetha harmonizing higher.
Imagine the production battle between the Bee Gees and Tretow sound! ABBA later had lots of problems getting Summer Night City right in the studio, so maybe the Bee Gees connection would have given them a useful disco lesson