You're right
under current rules.
Frankly, nobody knows what will happen or how far deportation will go, if even anywhere at all - but that in and of itself is the issue - pre-referendum, it seemed a fair assumption that EU migrants could live and work in the UK indefinitely - but now - don't know. Can't plan in an uncertain environment, and if you can't plan, you can't run your business.
We for instance use aws heavily - hundreds of thousands of dollars per year. We invoice our customers in sterling. That lost margin has to come from somewhere, which either means charging our customers more, or cutting costs. We'll probably have to do a bit of both, but this feels like stemming the bleeding while we figure out what to do next.
About ⅓ of our workforce are EU nationals - and few bother to apply for leave to remain, as it isn't necessary under current rules - so again, they no longer know whether they can remain here, and I wouldn't be at all surprised if they're considering moving on - why stay in an uncertain environment? They've already demonstrated a willingness to be mobile.