Well, at a first pass: Labor market negotiating power is unbalanced; owners of capital are loathe to give it away under any circumstances; workers, especially poor workers, don't have a lot of flexibility to shop around for jobs when they need one; and by and large modern business thinking & planning is incredibly short-term and liable to walk itself into stupid and avoidable situations like not being able to stock shelves with toilet paper for six months or sell $30k cars for lack of $5 worth of old computer chips.
Basically, you've got a pile of short-sighted, emotional apes, often operating under conditions of stress or duress, with imperfect information and a planning system that's effectively hijacking stress responses designed to respond to actual flesh & blood predators to evaluate interest rates. All that indicates to me that the cohabitation of "we can't find workers" and "no, we're not raising wages" is maybe less surprising than theory would suggest.
Specific to what's happening in the farm labor market, I'd suspect there's a lot of interplay between the immigration system being pretty broken and farm owners being on the whole kind of crappy businessmen that leads to this particular market distortion.
It seems like the explanation you're putting forward is: farm owners are suffering from too few farm workers but, because they are bad businesspeople, they don't realize that raising offered wages would allow them to hire enough people.
Any ideas?