There was a long period (post WW2 but mostly so in the 70's, 80's and 90's) when phonics was barely taught in UK schools at all thanks to the fact that whole word/look & say methods, which were widely used pre WW2 in the US, were seen as 'modern' and up to date and so enthusiastically adopted in the UK. Whole Word teaching had a particularly charismatic and influential 'guru' called Frank Smith who did a huge amount to promote and perpetuate Whole Word teaching and wrote some extremely influential books on the subject. Like many educational 'innovations' it was widely accepted and very little questioned.
The biggest problem with 'whole word' was that it failed to teach very large numbers of children to read. This inconvenient fact was blamed on many factors and whole word proponents had to try every way they could think of to get children reading without using the dreaded 'phonics' method. One way was to intensively teach the words which ocurr most frquently in written materials. The rationale being that if they represented a large percentage (50%+) of written text then children would be able to get the gist of what they were reading, even if they couldn't read everysingle word. Use of context and pictures was also strongly promoted to get readers to have a go at guessing the non-high frequency words.
One of the whole worders' biggest arguments against phonics was that the English language is highly irregular and that a large proportion of words cannot be decoded anyway.
Somehow, high frequency words and 'undecodable' words became irreparably associated in many teachers' minds, thus starting and perpetuating the myth that HFWs are not decodable. This myth is still going strong today.
It is entirely possible to teach a child to read with phonics without introducing any HFWs until teaching the graphemes that they contain. However, there are a few of them which are quite useful in early texts as they make the decodable text more 'natural' sounding. So, even good phonics programmes introduce a few of the most useful ones quite early on.
I have read Frank Smith's influential book 'Understanding Reading' (which, amazingly sells, 2nd hand, for astronomical prices on the US Amazon, but which I picked up for a fiver on UK Amazon) and can see in it the source of many current myths about learning to read. I am astounded that anyone took it seriously as it is full of very dodgy assertions and misinterpreted 'science', but, there you go!