I seem to remember from my schooldays that the feather and ball experiment has been performed in vacuo, confirming Galileo’s hypothesis. There are various mind experiments that are relevant (e.g. stuff feathers inside the hollow ball, so that it is now heavier and therefore falls faster). However, the main point is that the whole of gravitational theory fails if the hypothesis is untrue. The jocular reference to the old boy dropping things off the tower in Pisa was a misjudgement, as there seems to be no evidence that the experiment was actually performed.
Air resistance seems to be a red herring in all these arguments. For example the vertical velocity of the athlete is probably too small for this to be a significant factor. As one born with the duck syndrome, short legs, I had much occasion to observe that the predominant variable in athletics is leg length, so I turned to football (soccer).
David Scott, the commander of Apollo 15, famously performed the experiment with a falcon feather (the lunar module for the mission was christened 'Falcon') and a geology hammer on the surface of the moon, almost 38 years ago.
From checking the paper, it doesn't look like the authors are claiming that heavier athletes fall to the ground more quickly than lighter athletes. They actually claim the opposite - that heavier, taller athletes take longer to fall than lighter, shorter ones.
In the appendix to the paper which gives the background maths they take the time to fall as
t ~ (Lb/g)^0.5 where Lb is a body length scale, g is acceleration due to gravity
then they take Lb ~ (M/density)^0.3333 where M is mass of body
So that gives the fall time t as being proportional to M^0.16666. It looks like the longer fall time for a heavier athlete is coming from them being assumed to drop from a slightly greater height.
The paper also clarifies the point Frank has raised about the implausibility of athletes in ancient times having 70% less mass compared with today, they have 70% of today's mass or a 30% reduction compared with today.
The news media nowadays seems to take the view that there is a lot of overlap between environmental journalism and science journalism, so it makes me wonder whether the Daily Telegraph article was written by an environmental journalist standing in as a science journalist.