I didn't do advanced training after I passed my test... several reasons;- at the time it wasn't as prevalent, I didn't really have the money, & by the time I took my test I'd already been riding a 125 for 2 years & done around 40,000 miles... I'd already made most of the mistakes I could have learned to avoid from advanced training & thankfully only had one accident for my naivety. I didn't jump straight on a sportsbike instead going for big thumpers... I followed lots of bikes & spotted what I thought they were doing right or wrong & identified that in my riding where applicable. I learned accidents are potentially everywhere, avoiding them is the trick, while still having fun & making progress (my purpose for riding is to get to work, alive, to earn money).
If I was in that situation now I'd do my test straight away then advanced training almost immediately... & then, with only a maybe a thousand miles under my belt, set about learning how to ride a bike, but with a lot more knowledge of the possible pitfalls than I had when I did it originally.
Would I do it now?... Maybe I will, but I'd want to assess the rider assessing me 'cos we'd not necessarily agree... every rider has boundaries, limits that they won't stretch, theirs maybe very different to mine, but not necessarily wrong.
I note that the "Better Riding Guide" articles specifically don't have a comments section... at the request of the IAM?... there's certainly a lot to discuss but that in itself indicates the attitude of the group... "this is how it is... there is no discussion... end of".