Save the children are talking about an average child having 600 words at 2.5, but anyone (like me) who has asked for help with their 2yo will have been told figures of 50 or 100 words being the minimum average. So I can absolutely forgive 47% of parents who were asked picking out that kind of number when asked about averages. It doesn't reflect how well their child actually speaks.
I know when I first asked the HV for help (DS was 2.5) she asked if he knew 50 words. Yes I guessed he did, but less than 100 I thought (again a guess). Over the next week we write down every word he said or we could remember him saying and it was more like 150. So much better than we thought.
The SALT was much more interested in the way he spoke than how clearly or how many words - but building up vocabulary was supposed to help. I felt a lot of the SALT intervention was really about looking for physical problems, like autism - which is fine but if, as StC are saying poor speech in children who are NT/noSN is a problem it seems like SALT should be discharging those children to direct non-medical support, not just deeming them within average and telling the parents their child is fine.
However in our case it hasn't actually made his speech any clearer and his vocabulary is still not that great even though we do and have always done everything we could to encourage him. I have two girls that speak extremely well.
I'll be honest, I do think it's unfair to blame parents for being uneducated and not stimulating their child correctly when it's very possible they have likely been reassured along the way by HCPs that their child is fine.