What the quote from Guardian article says to me is that she is older and likely weaker. In that state, perhaps she has lost the form she once had. So, she slides some modern running shoes, which are like freaking orthopedic boots. She broke world records barefoot. She jogged the London marathon as a middle aged woman in shoes. Wow. Look, the best quote I read was some response/comment to the article in Competitor magazine that the OP linked to:
"Is there a reason elite runners don't run barefoot? Sure.
First, it would take elites a couple years, possibly more, to return to their current level in order to run barefoot; you can't just take off your shoes and start running; your feet have to develop; no elite wants to start their running career over.
Second, in the meantime, elites who run barefoot would not be able to secure shoe endorsements; what company is going to sponsor a barefoot runner? Nike?
Third, elites would also lose out on the prize money, a strong incentive not to deviate.
Fourth, as mentioned by others, elites already have great form and coaching, so barefoot running probably would have a high cost-to-benefit ratio; i.e. it would require too much time for too little reward.
Fifth, feet have to adapt to barefoot running. If an elite tore up the soles of their feet or stepped on a nail, an injury would sideline them for far too long. For most of the rest of us, the risk to reward might be worth it.
Sixth, elites who disparage running shoes in an article are not likely to hold on to their sponsors for long; they are more likely to give glowing comments about their shoes.
However, it could very likely benefit non-elite runners in that it may help us run correctly and thus more efficiently and thus faster.
So, for most of us concerned, it matters not whether elites run barefoot; it matters whether the risk-to-reward is worth it for us. If it is, then it might be worth it for the rest of us to run barefoot, at least until we run correctly.
And once we're as honed as the elites, we can choose to run shod again."