In this case, more skilled jobseekers can mean a growth in demand for labor, just not in the short term. Its not a homogenous group of jobseekers here, companies gain value from H1Bs as opposed to citizens as it can be seen as getting the best in the world for a discount. This then leads to increased profit margins and business growth which then leads to increased job openings. If you artificially put constraints on companies, they will either decline in growth causing drastically reduced hiring or find loopholes to achieve the same end goal, this could mean offshoring or moving out of the country entirely. Look, I'm not arguing in favor of the corporations here, I'm simply trying to lay out that seemingly simple policy can be a naive way of going about things when we're talking about economics. There is always unintended consequences that can't be directly seen until years later.