Yes, but the only reason you think that is because you understand the technical underpinnings (ie. the content is indeed being served by the same domain as the search results).
Regular users have been expecting search results to behave a certain way for over two decades. Opening the results in a modal is simply not the expected behaviour. Changing the back button is not the expected behaviour.
Regular users have been expecting search results to behave a certain way for over two decades. Opening the results in a modal is simply not the expected behaviour. Changing the back button is not the expected behaviour.