I suspect there is a lot of 'Defensive Instructions' about now. The companies and the NHS don't want to risk being held legally liable if their instructions/guidelines were less stringent, and a baby was harmed as a result.
I doubt that statistics exist, to show how many babies become ill when bottles were made and stored under the 90s guidelines, compared to how many get ill today. All I can say is that, when I was making bottles for my dses, I was following the guidelines as they existed then, and none of my boys ever got I'll from it. Nor were there lots of other babies being made ill by formula made up according to the then-current advice - not saying there were none, but I am sure that, if lots of babies had been getting ill and any of them had died, it would have hit the headlines - and as far as I recall, there were no such news stories.
Not statistically probative, I know - but relevant, I think.
It is my understanding that the current stringent guidelines were brought in after some deaths amongst babies in Special Care, that were apcaused by the bacterium E Sakazakii in formula powder - all the deaths were amongst babies who were already ill or weakened in some way - I am not aware of any deaths in otherwise healthy, full term babies.
I would like to pick the brains of those who are making up formula now, and know the current guidelines well. I was told not to level off the top,of the scoop of formula by scraping it up the side of the tin, as this could, compact more powder into the scoop, which could lead to over-rich formula. But a woman is shown doing exactly that (scraping up the side of the tin) in a formula advert (possibly Cow and Gate - the 'Take it from us, you're doing great!' one). Has that guideline changed, or is the advert showing bad practice?