Where do they come from, is the key. I presume they don't just magically appear, and are instead a real wild wolf who one day looks up, ears pricking, goes "hrrohrwr?" And sets off to find the presence it has felt and has an unstoppable urge to bond with across the miles, etc.
So, prior to its (shudder) imprinting, this creature was a bad mother. A random encounter waiting to happen one moonlit night. In other words, in a fight, it had the ability to choose for itself to attack, dodge, disengage, whatever. By becoming a ranger companion, it's formed a strong bond with the ranger. So it should want to protect it. The RAW kind of indicates, however, that, having trekked across the frozen river and negotiated the goblin forest to find its ranger bondmate, it puts aside its former life of tooth and fang and instead settles down in the corner to lick its balls while it's best bud gets beaten up by kobolds.
I know the bond has to develop for in game mechanic purposes, but...really? Ghost wouldn't let Jon Snurr get beaten up without being told to.
(All this is off topic, to be fair - in terms of can a wolf be gnome ridden it seems "yes" is the answer, so thank you. And I will apply the normal mount rules to the wolf in terms of dodge etc.)
I guess where the ranger needs to take an action to compel the beast to -for example - disengage, is because he has to override the beasts natural instincts to just flee or get medieval on yo' ass? My instinct would be for wolf to Help more than anything else ("My best friend needs me! I will snarl and nip at his enemy's ankles to distract him so my friend can make sausages out of him easier"). But. That's in a fight.