PHP Compatibility plugin marks Smartforms as not compatible

I’m in the process of deciding whether to upgrade my wordpress site from PHP 7.4 to version 8.x. To help me decide, I installed a plugin called PHP Compatibility Checker (from WPEngine), and to my shock and surprise, the tool identified SmartForms as being non-standards compliant with every version of PHP from 5.6 and up. Surely this cannot be accurate, as I have been using SmartForms for years (paid product, but my support agreement has expired). I would really like an explanation of why the compatibility checker (from a reputable vendor) is flagging SmartForms as non-compliant.