Earlier quoted context omitted.
There are more cyclists than young agile males. And your advice only applies to those. I'm trying to imagine a 60 year old lady on a bike applying this advice and fail to see any happy endings. And where I live old ladies on bikes are extremely common. Cycling advice should apply to all cyclists, not just to those giving the advice.
It's not about youth or agility, it's about skills and confidence. Young men innately have the confidence to ride assertively, but all cyclists should feel empowered to protect themselves. The obvious example is fatal accidents involving large goods vehicles and cyclists in London. Women are vastly disproportionately likely to be involved in this class of accident, despite being under-represented in overall accident…
All you should have to do to survive in traffic is to obey the traffic rules and the onus is on the rest of the traffic to give you the space you require in order to be safe. Anything less simply won't do.
Is this article the source of your claim?
http://www.standard.co.uk/news/london/women-cycling-in-londo...
If so I'd expect something a little bit more substantial to be presented as 'the leading theory', it's just a news paper article repeating a claim by a sports cyclist.
Lorries should be equipped with mirrors overseeing the area to the immediate side of the vehicle. And contrary to the statement in the article the safest place to be is not in front of a lorry but behind it, as a cyclist you should never ever go beside a lorry unless it is stopped and unlikely to move in the next minute.
After all, in order to get out in front of the truck you're going to have to be beside it anyway for a while (and how long will depend greatly on how fast you are moving, something a professional racing cyclist might over-estimate for the general population of cyclists.