In order to do this you must register your option pages with separate ID’s. There’s no mention of this in the ACF Docs but you can enter 'post_id' as a parameter when you use acf_add_options_sub_page or acf_add_options_page. Then you’ll be able to use get_fields('your_own_id') to only get the fields on that particular option page. Otherwise all option pages are registered with the same id: ‘option’.
To see what is happening you can use the function acf_get_options_pages() to list all your registered option pages and see their parameters.
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