The Southeastern stations near me do make it impossible when the ticket office is closed, yes. You can buy Boundary Zone tickets from a limited number of non-obvious online retailers (e.g. the forum's site or Avanti), but Southeastern doesn't sell them from its TVMs or online. Southeastern TVMs also don't let you vary the origin, because they have ungated stations and they do relatively little revenue protection, so they're understandably worried about short-faring. This means you also can't buy a point-to-point ticket in substitution for a boundary zone ticket at the departure station.
I know the railway likes to put about a strict interpretation of the requirement in the NRCoT to purchase 'a ticket' covering the whole of their journey before boarding if the opportunity exists to do so, taking this to mean any old ticket, not necessarily an appropriate ticket. Frankly, I think this attitude only strengthens the argument that TOCs can't be trusted with powers to prosecute people. They intentionally limit the range of tickets on sale at stations. And I know from experience that if you overpay and then ask them to reimburse you, they refuse. They still do all this even after the CAT finding on boundary fares.
Southeastern also have far fewer staff than they need to staff their ticket offices for the regulated minimum opening hours, and at single-person staffed stations they provide no cover for staff breaks, meaning you can't rely on ticket offices being open even when starting a journey at a time when the ticket office is advertised as being open.
Additionally, when they are there and they are open, they often refuse to sell you the ticket you ask for. I've had a ticket office in South East London refuse to sell an off-peak day return from Boundary Zone 6 to Maidenhead at 9.15am, when I was holding a Travelcard season ticket, on the grounds it was before 9.30am, even though I would have needed a warp drive to get to Paddington, let alone the western zone boundary, before 9.30am (not that 9.30 is even the relevant restriction on that ticket).
And only yesterday, they refused to sell me a boundary zone 6 to Maidenhead ticket because I tried to use a National Rail Travel Voucher as part payment, on the spurious ground that it was issued by SWR.
So yes, sorry for the long answer, but it is absolutely no exaggeration at all to say Southeastern refuses to make boundary zone tickets readily available. Short of having an actual policy of refusing to sell them, it is hard to imagine what more they could possibly do to make it difficult to obtain these tickets?
