Search_context_size seems no longer working

I am trying to use web_search_preview (https://platform.openai.com/docs/guides/tools-web-search?api-mode=responses) and set search_context_size to get different sizes of citations.
I have tried a number of queries and noticed that they returned similar number of urls regardless of the search_context_size that I specified.
In contrast, when changing this parameter in perplexity api, I do get different numbers of citations. Is this a known bug?