A firm's headcount is a dynamic value that is reflective of a rate of growth: its headcount is going up by x% each year, ideally linear growth or at least not a higher rate of growth than revenues or free cash flow. It requires an accounting perspective on the inflows and outflows of an ongoing process and not just a small slice of data. If you just look at that firm's hiring and firing in a particular year, subtracting the one from the other, you would appear to have shown that the firm was more or less simply replacing the other with the one. Yet, the main question for actually measuring the (firm and investor expected) impact of AI is whether that rate of headcount growth has changed without the stock price going down. That is, is it now proposed by management and accepted by investors that the firm will henceforth require less human labor in order to deliver on the present expected value of future free cash flow. You cannot infer anything about this question from the data shown.
There certainly is a separate question of whether a firm has changed its source of new hires, but that also isn't reflected in the data, which just shows approved visas against layoffs. For this, you would need to look at net hires year after year and prove that a growing percent thereof are H1-Bs.