I’ve only worked on it from a reserving standpoint, not a pricing or MGU standpoint, so I really don’t know how much the employer knows.
A laser can be applied to covered lives with very high costs - cancer treatments, chronic conditions, etc. I believe the stop loss provider has a limited number of lasers they can apply, and my understanding is that the aggregate deductible does not get increased by the amounts of the lasers (but hitting the agg deductible is not as common as hitting the spec deductibles).
And some contracts can be negotiated with no lasers - but those will incur higher premiums, naturally.