They are not going to change from 6mo, because the authorities know perfectly well that whatever age they set, the majority of people will cave and end up weaning a couple of months earlier.
If you say 6mo, the greater part of people introduce food at 4-5mo. If you say 4mo, people think they have been given the green light to start at 2mo and they begin putting all sort of crap in tiny babies' bottles etc.
The authorities in the UK switched to 6mo in the early 2000s because they were concerned at the numbers of people who were thickening very small babies' bottles with rusks, cereal, ready brek, puddings and all sorts of things based on a vague idea that this would make babies sleep better.
After they switched to 6mo, the numbers of people doing these (foolish) things have fallen a lot, which is exactly what the authorities were hoping would happen. Most people don't make it to 6mo, but the authorities don't really care whether they do or not. Giving small tastes of appropriate solids on a spoon at 4-5mo is unlikely to be an issue as far as public health people are concerned. They just don't want people force-feeding 8 week old babies with mashed weetabix and Farley's rusks in a bottle.
I started at 4mo and will do so with my current baby, for what it is worth.