An individual employee may do almost anything. But most of them won't decrease spending when given a raise. Some may spend exactly the same as before. The rest will spend more. Do those who spend more outnumber those who spend less? I have no data, but I would be astonished if those who spent less outweighed those who spent more.
That's not a claim that I make, nor one that I think is relevant.
What would I do with more income? Well, I'd probably save some of it, use some of it to pay down debt, and spend some of it. I don't have to be spending 100% of my current income for that to be true.