I don't think either is likely.
But guess what...
They care about one thing, dollars. If you are making them money, they will keep you no matter what. If you are not making them money, they will get rid of you. Pretty rational I think.
Corporations are run by people, and they draw on a huge variety of sources to make their decisions. Including, obviously, some that are not rational.
If women choose to forgo higher salaries in favor of something else, that's a different issue and it doesn't immediately mean that they are being "irrational", it just means they favor different things than men do.
If the hiring managers (of any gender) have an irrational bias towards thinking that women are not as effective as their male counterparts, this will affect the respective pay scales even within a competitive market.
Note that I'm not providing evidence or making a claim about the gender pay gap. I'm just saying that the claims you've made have many possible consistent explanations, including irrational bias against women.
And rationality of any one particular hiring manager isn't going to make a big difference; they still need to compete with every other hiring manager in the labor market and must offer something competitive accordingly.
Life is so good when rational arguments can hit a higher pitch than the virtue signals. ;)
But don't let facts stop you from repeating the same tired lies that have been debunked for years
http://www.politifact.com/punditfact/statements/2014/apr/09/...
It contains links to many more sources at the end.
Like wise the BBC being forced to disclose pay rates for talent some Male presenters have taken pay cuts btw
I mean, even if it's true that particular company is paying its women worse than its men, and even if legislation means they can't quickly fix it (I don't know how onerous this legislation is in the U.K.), the proper response on the part of any employee who is given these excuses ought to be "Look, that sounds like you have a difficult problem, but that isn't my problem. My problem is that my salary is $X when it should be $X+Y." Because at the end of the day their excuses aren't going to change the fact that they can either fix your problem or not, and if they don't fix your problem somebody else in the labor market can.
It's interesting because younger women hear the USA stats and complain about how they're being hard done by.
In both cases, it's because women choose to leave the labor force for a while, which makes them no longer like the men who made similar choices as them up until that point.