Southeastern High Speed Supplement

[Gwr12345]

I'm down in Kent next month, and looking at Travelcard fares into London. I've noticed that an off-peak travelcard routed not high speed has less onerous restrictions than an off peak travelcard routed via HS2.
Normally, with a change of route upgrade you'd pay the excess, but that would then subject you to the different peak restrictions, however, Southeastern also have the high speed supplements, which appear to be a separate ticket, not an excess. Therefore can a buy a Travelcard routed not highspeed and then buy a supplement, and benefit from the better restrictions?
I'd be travelling back on the Classic lines if that makes a difference.
Thanks.

 

[MrJeeves]

I'm not sure you've really asked a question, but everything you've said seems correct to me.

I remember hearing mixed experiences about trying to get a supplement when a routed fare exists or v.v., but I'm not sure which one was typically less likely to be sold.

In any case, I don't believe Travelcards are supposed to be excessed, so in theory the supplement should be the only option.