I finally got the 3.5 DMG and it seems to me to support level adjustment, not ECL per se -- this wouldn't be the first example in my experience where it's harder to figure things out using just the SRD (or where the books contradict themselves in places).
The drow Wizard 5 shown as an example on page 125 has five character levels, a LA of +1, an ECL of 6, and a CR of 6. Seems to me she has about 5,600 in gear, like a 6th-level NPC according to table 4-23.
Because the drow's ECL consists only of character levels + LA, this doesn't directly relate to a minotaur with one level of barbarian. The main possibilities I see are:
a) 2,500 gp (1 character level, +2 LA = 3rd-level NPC based on levels)?
b) 4,300 gp (CR 4 for monster + 1 CR for character level = 5th lvl NPC based on CR)?
c) 12,000 gp (1 character level, +2 LA, 6 HD = 9th lvl NPC based on ECL)?
Table 3-3 says an EL 5 encounter should yield 1,600 gp, and p. 55 says a NPC's gear is about 3x the average for a monster of its CR. 3 x 1,600 = 4,800, pretty close to b), and using CR to determine NPC gear value is consistent with the example of the drow wizard.
Adding gear to a NPC clearly makes it tougher. The DMG says that the extra reward compensates for the extra challenge. But it seems to me that a first-level minotaur barbarian is going to wipe the floor with a 5th level party if based on its ECL, it's got 12K of toys to play with. And any party members that survive are likely to have more treasure than they should.
So I think CR, not ECL, is the way to go; the SRD is confused because the two are more or less the same for NPCs that don't have racial hit dice.