The group have had two US top 10 albums, and their statement comes after two former partners of Signature Entertainment sued each other.
Mr Loeffler and music industry veteran Randy Phillips had launched the band's career, but split up and took legal action against each other last month over the group's management and control of Signature and another company.
At the time, Mr Phillips' lawyer Howard King alleged that Mr Loeffler had subjected the group to "years of mental and financial abuse".
 
According to Billboard in late August, the group were refusing to sign a recording agreement with Atlantic Records or perform as a group, until Mr Phillips was reinstated as their sole manager.
In a statement at the time, the group's lawyer Alan Gutman said they "support Randy Phillips the same way he has supported us from the start of our careers".
On Friday, Mr Loeffler's lawyer Michael Levin said Signature had profit share agreements with the members of Why Won't We, which had been "very beneficial for the individual members of WDW", earning them approximately $10m (£7.2m) in total.
He added: "Recent comments attributed to WDW members are untrue, hurtful, and apparently designed to be part of an ill-advised strategy to evade their obligations under these agreements.
"Signature would certainly welcome a reasonable and amicable resolution of this matter that preserves the mutually beneficial relationship that has helped WDW achieve their great success to date."