Yes Elfangor and Ax usually win one on one but I look at it this way: Apart from Elfangor being some kind of tail fighting prodigy both Elfangor and Ax were not just well trained, they were main characters.
Hork-Bajir aren't pushovers, and even if we say they're untrained it would still be a yeerk in the Hork-Bajir's head otherwise neither has any incentive to fight the other, so say we've got a good old fashion Andalite space cadet and a Hork-Bajir grunt, well Joe Andalite in the trenches meets Billy Hork-Bajir it's far less one sided than if Elfangor picks a fight with him.
Bare in mind in TAC Alloran, Arbron and Elfangor are all trained, Alloran's a veteran in fact, and still they nearly die fighting a group of Hork-Bajir on that transport ship, a group which honestly does not outnumber them by very much, certainly not by this boasted three to one ratio which I don't buy as anything more than Andalite propaganda (don't get me wrong I do recall it being in the books, I have a very strong sense that it was Ax saying it though, we know how unbiased his opinions are) Indeed it may have been because it was too confined a space. Elfangor metnions that he saves Alloran from getting flanked, Arbron states that Elfangor saved his life so you can't just say that any old Andalite could defeat a hork-bajir let alone trust that any trained Andalite could defeat three singlehanded when clearly there are times when that reach and speed aren't enough. Did the Hork-Bajir on the transport have experience fighting? Probably but how do you think they got it? By killing Andalites. Were they elite soldiers? Unlikely. Even if by some miracle they were, were they would be moreso than Alloran who nearly got his own butt kicked and still be serving on a transport so unimportant that the future Visser Three would have let it get blown to bits? Even more unlikely. So essentially to me at least the three to one ratio is little more than idealistic propaganda generated by Andalite drill instructors so their cadets don't freak out at the first sign of battle.
So obviously I take issue with the nine times out of ten ratio as well, it's far too one sided to be likely, remember the Hork-Bajir have been fighting the Andalites on the ground and in space as the Yeerk's number one shock trooper, if they were that ineffective the war would have ended before it ever reached earth, and remember the Hork-Bajir aren't slow, they're stated many times as being very fast themselves, and they have more endurance, they can take a lot more damage than the Andalites can.
So lets say you've got one Hork-Bajir, and one Andalite, if they're untrained but forced to fight to be honest I see it being advantage Andalite, but milder than 3 to 1, I would buy that in a one on one fight with none of the Andalite training Andalites would win against Hork-Bajir 60-65% of the time, it's more than half but by no means a sure thing. Mind you Hork-Bajir aren't just strong and well equipped, and they can take a beating. After the carnage of a battle with the Animoprhs it's often said that some of the Hork-Bajir they fought aren't dead, just unconcious, Andalites seem fragile by comparison, the worst we've seen Ax suffer is losing his arm and we didn't get to see how he reacted while it was cut off, maybe he went unconcious, maybe he grabbed it with his other arm and started beating the Hork-Bajir with it, we don't know, but I've never read anything that implies that Andalites could wrestle with a grizzly and still be breathng afterwards.