Actually, it's true. There are top cricketers who have failed as Captain like Tendulkar, but what he is saying that most of the successful Captains were among top few players in the team - not necessarily has to be the best player, but I am sure what it's meant by is that the player is an automatic choice without any doubt, if fit.
Tendulkar failed as Captain not because he was the first name in team sheet

, rather because his personality trait was reserve, he was a silent operator who would love to do his on job perfectly, but couldn't get the job done by others. There are many IT genius who are brilliant in developing software/hardware designs, but not good people managers and often creates problem in team. Tendulkar, Jaques Kallis are in that group. In fact, Sir Gary was a failure to be honest as Captain and KR Miller never got it. Also, most teams don't appoint their premier fast bowler as Captain to manage work-load - that doesn't mean Lilee, Roberts, Hadlee, Marshall, McGrath, Donald, Ambrose, Styen, Lindwall.... were dumbs or didn't draw respect.
But, most of the top Captains in history are among their top players - for Pakistan, Kardar, Mushatq, Imran, Wasim, even Misbah in his own scope took PAK to No. 1 on UAE based dominance and he has fantastic figures there. That's true most countries actually - may be you can name very few who were great Captains first, player second - Brearley, Illingworth, Tony Lewis, Darren Sammy, Ali Bacher...... However, many of those such Captains are English because ECB/TCCB had a different policy of appointing Captain - Royalty, OxBridge blue, amateur ......... these were major criteria for appointing Captains hence we have seen Lord Haris, Plum Warner, Gabbi Allen, Jardin, Lewis, Brearley, Walter Robins leading England but Hobbs, Sutcliffe, Tate, Larwood, Compton, Pynter, Sandham, Verity .... didn't, even didn't lead their Counties. SAF also, had different criteria hence some of their great Captains made the XI as Captain first in olden days. Before WW2, WIN captains had to be white - that was first qualification... and before partition, India had some Maharajas as Captain, basically for their connections and funding of the tour.
Australia has always appointed someone Captain you would remember the name - I did, even after 125 years - George Giffen, Monty Noble, Vic Trumper, Clem Hill, Warwick Armstrong, Bill Woodful, DG Bradman, Lindsay Hasset, IW Johnson, Richi Benaud, Bobby Simpson, Bill Lawry, Ian/Greg Chappell, Graeme Yellop, Kim Hughes, A Border, Mark Taylor, Steve Waugh, Adam Gilchrist, Michel Clearke, Steve Smith .... finally this WK guy.
I hope Babar proves me wrong, but if he is appointed Test Captain now - in two-three years time he might be humiliated at PP - he won't be able to match the "expectation" ....... Sarfraz didn't last 2 years after winning an ICC event. But, that has noting to do with the best player being appointed as Captain.
For PCT, with the current state of the team and possible future few years, best thing is to appoint someone Captain with THICK skin, deaf ear but great mouth and whose lack of performance won't cost team that deadly - only guy I see is Shan Masood..... the punching bag.