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Again, your interpretation yields the unreasonable result that a building might be allowed to have two feeders for one of the allowed reasons (225.30), or two services for that same reason (230.2), but one service and one feeder would be prohibited.
I'm not following you here.
Note the phrase 'on the load side of the service disconnecting means' in the second adjective clause of the first sentence in 225.30. And note how that phrase is
not repeated when 'feeder or branch circuit' is repeated later in the sentence.
The meaning is: Where a feeder or branch circuit supplies a building from service equipment that is
not at the building, then no other feeders or branch circuits shall supply the building
whether or not their service disconnect is at the building. (That is, unless the other specific allowances apply.)
As far as 225.30 vs. 230.2, only 225.30(A)(8) is at stake. (Docks and piers). Because you're not going to find EV equipment listed for more than one service, and the list of special conditions is otherwise the same. I don't see any unreasonable result.
Per the scope and the structure of 225, it can not and does not regulate services. While the title of 225.30 is "number of supplies" without immediate qualification, the title of Part II just above that is "Buildings or Other Structures Supplied by a Feeder(s) or Branch Circuit(s)." That qualifies the meaning of the word "supply" in 225.30 only to supply by a feeder or branch circuit.
The existing branch circuit puts the OP's garage under the scope by any part of what you quoted. The new service violates the section in its own words. One doesn't even have to look at 230.2 to conclude this, although looking there also finds a violation.