Yeah, I would just about agree with that definition. Jollop would generally mean a medicine intended to either open the bowels, to close them, or to promote expectoration. Chemist's proprietary medicines were frequently coloured & flavoured with liquorice or caramel, hence commonly brown of hue, like over-stewed tea. A strong, preferably nasty, taste was held to show it was 'doing you some good'.
Tales of bromide and saltpetre (sexual urges for the reduction of) being added to forces tea are often told.
The repeated line "Tell me boys, have you any complaints?" is a reference to the orderly officer's regular visits to check that there were none. Spike Milligan recounts the following exchange in his memoir "Adolph Hitler, My Part In His Downfall".
Officer: Any complaints?
Soldier: Yes Sir, it's this.
Officer: What's wrong with 'this'.
Soldier: Nothing wrong but what is it?
Officer calls the head cook.
Officer: This man wants to know what this is.
Cook: That Sir, is a 'Frappé Mystique a la Aldershot!'