Blood tests take time and money.
When a child first presents with symptoms, parents will got to their GP. Who's not an expert in all these esoteric conditions.
As my Mum's GP said to her when I was a few weeks old - "your son can't have [insert genetic condition], it's extremely rare, and I've never seen a case of it".
And at least in the UK you have to get a GP referral to see the actual specialist who can diagnose that yes I do have that rare condition. And the reason my GP had never seen it before was because it was, of course, rare.
So in this case a simple but not very reliable tool to help narrow down possibilities might be useful. As long as it's not giving out so many false positives that the specialists can't get any work done.
The other downside of having a rare genetic condition is that there aren't many qualified doctors you can see. So the last thing I want is all my possible appointments used up by some AI causing GPs to send half their patients in for checking. To be fair, with pointers in the right direction GPs can usually look up what tests they need to do, their problem is just that they're generalists who don't see enough of the odd cases to be able to recognise them without a hint.
For example I ended up in A&E having an X-Ray on a wrist injury a few years ago. And had to wait an extra ten minutes before finding out if it was broken so the doc could use me as a quick exam question for his students. So there's 5 doctors who should be slightly better equipped to do that diagnosis in future.
Not that I'm convinced this AI thing will work, but it could be capable of doing just enough to help GPs a bit for very little cost - so I can see it being quite successful as an approach. Maybe. If they can get it working reasonably well and still persuade users that it's only an indication not absolute truth. The second maybe being a harder job than the first?