Apologies are always difficult. There's always a fine path between the Scylla and Charybdis of saying too little and saying too much (do we really need to know...?. Then there's the question of whether you seem sincere or just mouthing it. There's hundreds of times we've heard people say "I am very sorry if I upset you over this" (carefully not, "I am very sorry to have done this"): good enough or not?
In a way, too much scrutiny of the words is perhaps beside the point. Apologies are rituals, they are a very simple case of "doing things with words". The only thing that actually counts is the audible expression of "I'm sorry" (like "I do" at a wedding). Or are we expecting people to SHOW contrition? And how do we recognise it, in any case. Some people can seem dead truculent and controlled but actually be eaten up inside -- and vice versa.
That is in a way Maria Miller's problem. My guess is that the party spin doctors instructed her to be as brief as possible, on the basis of "give the press any rope and they'll hang you with it", and I might have advised that too if I'd been a spin doctor; wrong call as it turns out. Not that prolixity (so far as I have been able to discover) is the trademark of House of Commons apologies. Nadine Dorries was no longer (even shorter) than Maria Miller, and David Laws a bit longer, but certainly not essay-length (it's the second, shorter one here).
But there are worse sides to public apologies and they can lead in dangerous directions.