What they told is you blatantly wrong. Every math formula that works in Acrobat should also work in Reader. Only things like extracting pages and stuff like that won't work there.
Did you test it on a mobile device, though, or on a regular PC? Unfortunately, many scripts won't work on the former, regardless of it being Acrobat or Reader.
Third-party viewers are a completely different question. You can't guarantee it will work in them, at all.
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