An answer might come from a broader realization that the computer rarely stumbles over anything but a lack of information.
For example, Scotty somewhat infamously asks the Holodeck to produce an image of the bridge of his old Enterprise. The exchange is as follows:
Computer: "Please enter program."
Scotty: "The android at the bar said ya' could show me ma' old ship. Lemme see
Computer: "Insufficient data. Please specify parameters."
Scotty: "The Enterprise! Show me the bridge of the Enterprise, ya' chatterin'
Computer: "There have been five Federation ships with that name. Please specify
by registry number."
Scotty: "NCC-1701. No bloody A, B, C, or D."
Computer: "Program complete. Enter when ready."
The computer is not able to tell Captain Scott which ship he wants to see; however, it is able to parse out the colorful language without mistaking it for a command it isn't aware of. It also permits him to draw out the lengthy "no bloody A... B... C... or D.", so we know the computer can also continue to incorporate the continued dialog of the user; it isn't bound by the parameters of pre-defined functions and it isn't just looking for keywords - it comprehends your English and derives a meaning from it.
There are other times when it does similar tasks; most notably, it allows a user to compound queries by saying "and" or "now" to extend the nature of the original request. It maintains context for the requests, and allows for indefinite articles to be used to reference points of data. From the episode Transfigurations:
DATA: Computer, run transformational matrix calculations. Match
navigational referents to known stars in this sector.
COMPUTER: Information on this sector is incomplete. No correlation.
LAFORGE: I'm not giving up yet. Not after coming so close to cracking
this thing. You know, that might be flight path information from John's ship, but without a frame of reference, I can't determine its origin points.
DATA: Computer, assume those paths are course corrections and derive
gravitational values for stellar objects near those flight paths.
DATA: Most of these are ordinary G-type stars. This would appear to be
a neutron star, possibly a pulsar.
LAFORGE: Which means that this might be a rotational time reference.
DATA: Computer, assume these symbols are pulsars. Translate associated
values into standard temporal notations. Computer, is there a pulsar
with a rotational period of one point five two four four seconds
within sensor range?
LAFORGE: Bingo! Now, Computer, overlay navigational chart using
referenced pulsars and project a flight path back to its origin.
COMPUTER: Flight path originated at bearing zero zero three, mark zero
one five. Distance, two point three parsecs.
Finally, let's assume that in all cases when an entity with computer access addresses the computer, the universal translator is at work. This would mean that the computer accounts for word order, syntax, inflection, and so on. In English, one can structure a sentence in a variety of ways: "I'd like a taco." "A taco, please." "I could sure go for a taco right about now." The computer never really seems to trip over the structure of a person's sentence - the meaning is typically always inferred, and if the user needs to narrow down the selection through a series of continued decisions (such as Tom Paris attempting to order tomato soup), the computer guides them down that path.
TLDR -- the computer constantly demonstrates the ability to encapsulate an entire conversation within the context of queried results from the database, and also demonstrates its capacity to filter verbal garbage out while also comprehending the user's intent. As long as Captain Picard doesn't low-talk and horribly mangle his request by intentionally obfuscating the meaning, he can ask for tea in any number of ways.