spend is a noun in this sentence. As a noun, spend refers to the amount of money spent for a particular purpose or over a specified length of time

Spending is also a noun. A gerund used to be the way you nounify a verb. “Ad spending” is perfectly grammatical, unlike “ad spend”.

This seems to be part of a broader trend, not just business. One group of pastor-students would talk about giving a “preach”. Drove me nuts.