I would agree with that plus if there is under-reporting then it's likely to be to a similar percentage level for all unions, at least all similar unions, so wouldn't really change the picture.
The main problem in Scotland is, and pretty much always has been, is the amount of rugby played in state schools. For too long there has been a preconception here that rugby is for public (private) schools not state schools. Certainly, there have always been some very good exceptions to that rule amongst state schools, and certain areas notably the Borders have faired better than others, but there is a shortage of youngsters coming to the sport through school despite the SRU's considerable efforts.
We had a couple of Scotland players come round every primary school in the town just before the summer break when I was in my final year at primary. When we moved to secondary after the holidays, the options for playing rugby were minimal. There was no rugby team for the junior school boys and although the girls managed to petition for a girls team to be set up, it was cancelled after a month or so because the numbers weren't high enough (hardly time to build interest). Within classes, it was 'taught' for 4/5 weeks per year (when not cancelled due to bad weather) and only to the boys. The situation at the same school is even worse now - my cousin is now 17, I took him and some of his friends to their first few Scotland matches just before he started his standard grades (studied for two years from 14-16). Enthused by their trips to Murrayfield, he and his friends asked the Head of PE if rugby would be included in the Standard Grade curriculum. Despite choosing PE as one of their standard grade subjects, meaning they'd be committing to around 6 hours PE per week (including the mandatory 2-3hrs), they were told that there would be no time for rugby - at all! And all after hours rugby teams have been scrapped. These were all members of the school's basketball team, so had at least good hands, and were all keen to get involved but went through their entire time at school without ever once being given the chance to try rugby. Funnily enough, I see the same Head of PE at Murrayfield, or on the train home, a couple of times every season - I'm often tempted to start a debate on rugby in schools on the train with some particularly drunk and rowdy forwards, then point him out!
It's just one school but as example it shows the issue. It must be very intimidating, and requires a big step up in interest levels, for a kid whose not got family or friends in a club to pitch up and join if they've had zero experience of playing the game and it certainly dissuaded my cousin and his friends from doing so (plus the town's club is just starting to recover from years of rather patchy existence). Not every kid goes to university either and if you've not got them participating by that time, the chance of getting them involved at all is minimal and the chance of them choosing, or having the option of, rugby as a profession is gone.
Around the time of the latest revamp in the SRU's regional development policy, I was working for a neighbouring local authority so got a couple of chances to chat to the guy responsible for this area - his enthusiasm and commitment are not to be doubted, and he has helped greatly with the town's club, but unless he and his colleagues across Scotland have the backing of schools and teachers, their impact will be severely limited.
The role of the Scottish broadcasters has to be considered also - their coverage outwith the AIs, RWC and 6N is abysmal. Magners League matches shown only on a Gaelic channel which is available only via satellite or online and which does not provide English alternative commentary, or cursory late night highlights with no summary, interviews, etc. Radio coverage is not much better - Radio Scotland only provide this when they feel like it and not if it'll mean Tammy McHalfcut fae Inverpubahunnermilesfaeglesga's views on that weekends Old Firm matches aren't heard. There was no live coverage, TV, radio or online, of either team's Heineken Cup matches this weekend and we'll be reliant on ITV national, with its understandably English bias, to show highlights on its most minor channel - we'll be lucky to get 2 minutes per game. Without regular, promoted and accessible coverage, which the SRU are prepared to pay for let alone give away, then getting people enthused, inspired and participating is an uphill struggle.