If the equity pool is at the operating company level, all investors are diluted equally, which is typically why creating such a pool requires an elevated voting standard for approval. But the investors still have their preference which will get paid before any employee equity. In the VC context typically they will require an equity pool reserve up front for the startup, which dilutes only the founders and existing investors before they come in on top of that, but I haven't seen that in the search fund context.