I subscribe to the theory that status (or dominance) in dogs is very flexible instead of rigid (like wolves). Dogs can be of different status at different times and places. For instance, we have two dogs that will fight immediately in the house…but they will happily walk for miles next to each other on a walk. It can chage due to life changes...a sick dog will be challenged for status immediately...a bitch in heat will be very protective of her status. Some dogs couldn't care less about status...some can't think about anything else. Things that provoke status fights are usually about space....the best sleeping spot, the best sun spot. And they are easily triggered when dogs are aroused...so when they are jostling around at the door waiting to come in ou out. Sometimes a status fight will be brewing for a while...and if you are attuned to it you can see...a lot of staring at each other,a lot of stiffening when the dogs approach or pass each other...sometimes there are very few calming signals being given (turning head, licking)...I think the reason you don't see the calming signals is that both dogs really would like to have it out to see who really does have the higher status. It seems like the fight comes out of nowhere.
Sometimes one dog doesn't really want to fight, they just want the other dog to stop seeking higher status...so then you will see a lot of calming signals, lick lipping, lip curling, growling and a fight can be averted either by the dogs, or human intervention.
Personally, I don't have any experience with a male/female pairing having relentless status fights...I would imagine it isn't too common....most opp. sex pairings can sort out their place pretty easily. And often one of the dogs will guard resources against the other...but that doesn't really have all that much to do with status, particularly if the dogs do sometimes trade back and forth.
That's my take on it...I am no expert, but I do a lot of reading