Well now you know. They are old schools that have survived due to certain practices, some are more relaxed than others but some are very strict in their entry and conduct requirements. Although "cult" is rather distasteful, in someways it's probably not far off. Koryu are specific institutions, organisations. As soon as someone says "this is koryu" then the question they will be asked is "which ryu?". A ryu is very specific, each one has it's own outlook, practices, traditions and even terminology. Koryu maybe an umbrella term but they are very rarely discussed in general terms because you are more often than not always talking about a specific school.
I think we were approaching that sentence from different angles. I was looking at it from the perspective that the most important criteria for any MA should be 'does this work' not 'where does this come from'. As I understand it you and Gary meant that only something of a particular lineage (and limited to that lineage) can be called a koryu.
They are layered systems, with things being disclosed as you progress and as you earn trust. Things are sometimes deliberately hidden. So you might well be doing one thing but you don't get told the actual reason for it until latter or it's changed. A good example might be targeting as in something like Tenshin Shoden Katori Shinto Ryu or look at how some schools perform embu. Things will be deliberately altered. With that in mind how does that bode for someone teaching it to others? Actually IIRC the heads of the various koryu are in fact legal owners, in Japan, of their teachings. Now of course a wrist lock is a wrist lock but the strategies and concepts behind it's delivery may well be specific to a certain school. So where does that lock become the lock from that ryu and where does it, for example, end up being a poor Aikido kote gaeshi? Can you say for certain what you are delivering is from a koryu? Can you be certain it is true to its source? This is the thing. Waza are there across the board so where can you say "I teach this from x-ryu"? If you aren't sticking to the teachings of that school? It doesn't have it's origins in it, the origins could well be the misguided understanding in your head. Again due to how many of these schools function. Indeed.
But the fact (and I do mean fact) is that the word in Japanese is an umbrella term. If Macko had identified a specific school in his post, you would be justified in asking him to elaborate on his meaning, but he didn't, he used the umbrella term.
Takamatsuden would be a good example, multiple ryu all very closely linked yet each one with its own flavour.
He followed it up with mention of what is being taught is "aki-jitsu based, daito-ryu syllabus.". That's specific enough and what promoted my initial post and follow up to Gary's question.
Which isn't a koryu. So is your argument that you can't teach old style techniques with new style techniques? Because that would blow my mind.
No that's not my argument. My point was that it's not koryu. He mentioned what the system was, I pointed out it's not koryu. My other points were that if you are claiming to teach a koryu or something from one, then you need to be able to show it because of how they function.