Actually, you could make that case for Don Henley, but not for any of the others- Jack Bruce split vocal duties with Clapton, Lindsey Buckingham and Christine McVie were two of three singers in Fleetwood Mac. Glen Hughes was never the lead vocalist with Deep Purple and split the job with Joe Bonomassa in Black County Communion
Jack Bruce was the main vocalist of Cream, Clapton sang very few Cream songs. Fleetwood Mac was a 3 headed vocal monster all of them are equal in my book.
Only when he was in Humble Pie, he was the lead guy on his own. Steve Marriott was the main vocalist in Humble Pie.
Jack was lead vocalist on the first album (Fresh Cream) by Disraeli Gears, they were pretty much 50/50. Jack sang a few more leads on Wheels of Fire, and maybe one more than Eric on Goodbye. This was by design, as the record company was pushing Eric to sing more. I do think that Jack was the stronger singer- and songwriter as well.
Reread the criteria of the op, McCartney was the lead singer and frontman but he is also rated as a top 10 bassist by Rolling Stone.
Not the frontman but is a good player and can carry a song vocally per OP. That disqualifies McCartney. Has nothing to do with being a top 10 bassist.
The op said “I’m not talking about the frontman who once in a while picked up an instrument”.
