Plenty of pious codswallop about "not cricket", "mean habit", "not playing the game", etc etc. I am surprised that no-one claimed it is "ungentlemanly behaviour, by gad"! As to the OP "getting caught" - for doing what exactly? Even mention of potential fraud. However, as far as I can see, nobody has pointed to anything in the DR scheme rules that actually says it is not allowed. You play a game by the rules, and as far as I am concerned, if something is not against the rules, then you are entitled to it. The DR scheme rules are already sufficiently stacked against us, so why voluntarily stack them even higher against yourself? As far as I am concerned, whether I am entitled to 5p or £5, I will claim it. If others choose not to claim money that they are entitled to, that is up to them.
As far as I can see, the rules state that you are entitled to have two tickets considered as one journey - but that does not mean that you are REQUIRED to consider them as one journey. For example, if I buy a ticket to travel from A to B this morning, and another ticket to travel from B to C this afternoon, does that mean they HAVE to be considered as one journey? Of course not. It is my decision whether I am making one journey, or two. If I am delayed arriving at B, such that I have no time to do my shopping, say, so decide to travel straight on to C without break, then I would feel perfectly entitled to submit a claim for the delay to my A to B journey. And if I were then further delayed travelling from B to C, I would feel perfectly entitled to submit a claim for the whole journey A to C. And yes, that is "having my cake and eating it" - I like cake, and if I am entitled to it, I see no reason why I shouldn't eat it.
As to the suggestion that you are only entitled to consider them as two separate journeys depending on how long a break there is between them, can anyone point me to anywhere where this dividing-line (below this time is one journey, above is two) is defined, as I can't find it.
So to answer the OP's original question "can I still claim delay repay on the A-B ticket?" - the simple answer is "Yes". Of course you can submit a claim. Provided that you consider them to be two separate journeys, I can't see that you are breaking any rules. Of course this is "gaming the system", but that is what systems are for.