"To take part you just need to spend 15 minutes in a sunny spot - a playground, local park or residential garden, … ". So it is a measure of the abundance of the subset of butterflies you get in gardens, not the full spectrum found in the UK. And don’t Red Admirals migrate here when the weather and winds are favourable? So their numbers tell us nothing about the state of UK habitats.
Yes: there was, I believe, a large influx of Red Admirals around the time of the survey. And yes - as with the bird survey, results are not from a true mix of habitats.
A huge number of fresh Red admirals here a month ago
Nettles are very much reduced this year.
So what will next year bring…
Yes, as is often the case, a misleading headline without any nuance or context. Unfortunately, many people will only read the headline.