The Wind Walk spell allows creatures to assume a "gaseous form" that enables them to fly very quickly:
You and up to ten willing creatures you can see within range assume a gaseous form for the duration, appearing as wisps of cloud. While in this cloud form, a creature has a flying speed of 300 feet and has resistance to damage from nonmagical weapons. The only actions a creature can take in this form are the Dash action or to revert to its normal form.
Unlike the spell whose actual name is Gaseous Form, the gaseous form of Wind Walk doesn't say anything about various abilities that might be enabled by being non-solid, such as entering another creature's space or squeezing through small cracks. However, many of these abilities are implied by the term "gaseous form", even if you don't read it as a reference to the spell of the same name.
So, does Wind Walk actually make an affected creature non-solid and allow them to do anything a gas could, similar to Gaseous Form? Other than a very fast fly speed, what additional abilities, if any, are granted to a creature by Wind Walk?