No, what you're talking about isn't the meaning of words, you're talking about judicial continuity.
On meaning of words, its really quite clear. Although there are slight variances between dictionaries, "sex without consent" is the basic common thread. There is a disconnect between the meaning of the word and the offence.
Judicial continuity is not unimportant, but it should never be an end unto itself.
In fact, it hasn't been. The law on what is or is not rape has changed as recently as the 1990s (the common law "marital rape exemption") being abolished.
Re. your reference to 2003 - yes, the SOA was (another, more comprehensive) overhaul - not just adding anal and oral, but also redefining consent. Harking back to the 1400s to lend some authority doesn't really work when the definition has never been entirely static. It will almost certainly changes again, at some point.
There is no reason why would couldn't have additional separate offences under the umbrella of "rape", for better continuity of tracking (in fact, there are already two separate offences that both use the term, those under s.1 and s.5).
I think its time for law to catch up with plain meaning.