I think it's a brilliant idea not to have post counts in General Discussion.
There are a lot of people who think having a high post count makes them sort of "well liked" or "well respected" on forums - as Mick points out.
There are also a lot of people who think if someone with a high post count answers their question on a forum - the answer they are giving is more reliable because of the high post count.
This is a phpBB support forum, people visit this site for support with their phpBB forum, they don't rock up here just to chat and for that reason, if they post a support question and it is answered by someone with 5k posts - most of that posters 5k posts are phpBB related so they most likely know what they are talking about.
Now imagine they come and ask a question and it's answered by someone with 5k posts - but only 10 of those posts were to do with phpBB and the rest were random chatter - the poster is going to think what a shoddy support forum this is.
This is why the majority of software/product/business support forums do not have a General Discussion forum, members are encouraged to keep to the topic of the product, this avoids having pointless topics or people looking for illegal advices etc, could you imagine some unscrupulous character getting arrested for having illegal files and saying 'the guys on phpBB told me how to do it anonymously'
Other discussions can be had via the PM system - though some business's don't even allow PM's because if the advice they are being given is illegal - if it's in a PM they are still using that business's server.
This very site has a few political discussions in General Discussion - they all turn sour, it lets users see who is a Democrat sympathiser and who is a Republican sympathiser... which can cause a divide because some people are funny about that sort of thing, they will ignore the help of someone who supports the opposite political party - so if the support forum is about the product only... you avoid all this nonsense and pointless arguments.
It also benefits the search system too, being able to search for product help without pointless General Discussion topics appearing in the search results makes things a lot easier for the end user.
I dare say there have been people in the past and will be people in the future who have joined this very site who don't run a phpBB forum, have never ran a phpBB forum, have no interest in starting a phpBB forum, know nothing about phpBB so can't offer support but just signed up to chat - it's totally right that they shouldn't have a post count because they aren't contributing help towards the product.