That situation isn't restricted to Absolute Block. You can find it on lines worked by Electric Token Block or Tokenless Block, and even Track Circuit Block.
Swinderby is an excellent example – almost the textbook Absolute Block layout (until the crossover was removed at least), but actually Track Circuit Block both ways. I hear so much nonsense ("a little island of Absolute Block", "it's got semaphores so it must be AB", etc.)
Then how do you categorise those sections that are defined as Absolute Block in the Sectional Appendix and are provided with ordinary block instruments, but don't require the physical observation of tail lamps because there's continuous track circuiting through the block section?
Or the block section between Dinting and Manchester East (now a workstation in the ROC) with two "train arrived complete" plungers for the latter!
So what to block instruments show with intermediate block?
The same, but the block section doesn't start until the intermediate block home signal so you don't *need* a line clear from the box in advance to let a train up to that signal.
Also of imterest here is the arrangements when switching boxes out, say at night, and ensuring that only one train can be in the longer section during the switching out procedure.
You can't have a train in the section on either side, on either line, when you're switching out – presumably for that reason.
You can switch in with a train in section, but the same risk doesn't exist – you know there's one train in the longer section, and once you've switched in, there's one train in one of the two shorter sections, you just don't know which one (unless you've just seen it pass) so you don't knock out until the box in advance does or you see the train pass.
Also the arrangements where absolute block controlled by a signalman with his blick instruments, bells and levers joins onto an track circuit block controlled section. Hellifield to York power box at Skipton is a good example.
Nothing complicated. You work AB one way and TCB the other, as simple as that.