Workplace nursery scheme - what's the trick here?

My wife's company has just got a new benefits programme and one of the options is a 'workplace nursery scheme' where you salary sacrifice the cost of your nursery and the employer pays the nursery direct (saving income tax and NI).

This is the first time I've heard of this for nursery having had several jobs with 'flexible benefits' - it's different to the old voucher scheme and the government run tax free childcare (which is limited and a massive pain). Obviously the salary sacrifice aspect is similar to pensions or electric cars or cycle to work etc.

I understand the basic idea here but the weird element is that the company pay the nursery an extra £100 a month and you have to have a phone call with the nursery (and the people who run the scheme, who I assume take a cut of this) at the start of the arrangment where you discuss how that money will be used - on the call you are acting as an 'agent of the company'.

I'm assuming this is legitimate and the extra money and phone call is exploiting some loophole (for want of a better word) but what exactly is going on, any ideas?