This is standard behavior for <input> elements on mobile browsers and not an Algolia-related behavior.
Customizing the CSS media queries to enforce a minimum font size on mobile devices is widely considered to be best practice.
Though you can also make customizations to your HTML with a user-scalable attribute, this approach is no longer supported by Safari because it prohibits accessibility.
Please refer to this non-Algolia guide from W3 for a comprehensive discussion of the topic and suggested solutions.