I don't think it does depend on perspective, blankie. Or no more than it's a matter of perspective whether your employer should expect you to work for free on weekends, or during your annual leave.
OP raised a couple of issues: extra home-working tagged onto KIT days. They need to treat all the days you work during ML as KIT days, whether or not you're in the office. And if you are required to come in for part of a day, they need to treat that as a whole day and pay you accordingly. If they'd made it clear that this was a whole day's work, of which half would be home-working, then maybe what they've given you would be fair enough, but If that's what they intended, I don't think they've communicated it well at all. If they are paying you for a half day, they shouldn't be, even if they didn't set you extra work on top.
Blankie's post raised a couple more: you should have been paid for KIT days on top of your maternity pay. These things aren't an exemption for your employer from paid maternity leave. If they want you to work during your maternity leave, they pay you extra, otherwise they're just cheating you of your leave allowance, and getting a few cheap days work, as most of us don't get full pay throughout maternity leave. KIT days can be great for keeping you informed about changes in the work place... That is what they were intended for. But both employer and employee need to treat them in the spirit they were intended, otherwise they will just be an extra pressure on women (and men) to work beyond what they're paid for. Blankie, maybe you do voluntarily work weekends and holidays as well, and in one sense, that's your business. But I worry that you might be setting a benchmark that other people will be expected to live up to, when they most certainly shouldn't have to.