It is a shame I don't have my favourite book here to take a look, but I recall that in all cases of stability (longitudinal, lateral and directional) less speed meant less stability, for a variety of reasons and effects.
The crosswind, of course, does not affect directional stability.
The most important thing about airliners' directional stability is to know that the fin is capable to cope very well with gusts. So much so that if, at any speed, we use rudder to arrest a lateral gust we can lose the fin, along with our lives.