No, it doesn't necessarily mean that it was second hand. I have never known a Steinway D to sit in a showroom for 5 years unused though. I don't know how things were economically for Steinway or the USA in 1972-77, so I don't know if an instrument would have sat on a showroom floor for all that time. It's likely the piano was a concert hire instrument and was put into stock after 5 years of hiring.
It's not unusual for musicians to buy used Steinways even when they can afford brand new ones. It's likely that Freddie would have been looking for a piano with a clear and cutting sound that would work well in the band situation. Yeah I know they mic it up with helpistill pickups, but the tone still has to be bright to start with.
Glenn Gould and Horowitz both had used instruments because they liked those particular pianos, both could well afford any piano they wanted.
miraclesteinway