Yes, there'll be employers who use it in different ways, I am sure that some people are exploited.
I get my hours for my working week on the prior Wednesday, I'd like them 7 days before because I have to give 7 days notice of days I cannot work, getting them on a Wednesday means I can only reject Thurs/Fri......... if I'd like to. I get holiday pay built into my hourly rate, I think it's 1 hour per 8 worked, I also get 1:5 times pay after 8pm and weekends so I regularly choose the 4-midnight shift enabling me to cycle during the day and a 12 hour shift on a weekend. Bank holidays are 2x. I'll often work only 4 days and be paid more than regular contracted 37.5 hour 5 day employee. And I am still as "free" as when I was self employed, I don't have to ask my employer for days off should I see a cheap flight I want to book, I just book it and then tell them.
I don't want to work full time, I don't want to be tied down to a 9-5 job, I want flexibility and freedom, my contracted workmates don't get it, they'd be scared to death of not having the security of a guaranteed salary, but I was self employed, so what's new? The negative is no sick pay, but then I don't get sick like contracted employees seem to do.......
What I am experiencing seems miles away from what I read in the earlier post regarding Wetherspoons.
For it to work well, both employee AND employer have to be reasonable.