Installtool-Check "checkMaximumFileUploadSize" doesn't look at BE/maxFileSize, but message suggests that
If the php-setting
upload_max_filesize is less than 10MB (10 * 1024 * 1024), the following message appears:
PHP Maximum upload filesize too small upload_max_filesize=8M By default TYPO3 supports uploading, copying and moving files of sizes up to 10MB (you can alter the TYPO3 defaults with the config option TYPO3_CONF_VARS[BE][maxFileSize]). Your current PHP value is below this, so right now, PHP determines the limits for uploaded filesizes and not TYPO3. It is recommended that the value of upload_max_filesize is at least equal to the value of TYPO3_CONF_VARS[BE][maxFileSize]
This message suggests that the maxFileSize is relevant here, but in fact it does not influence if the message appears, only the
upload_max_filesize is relevant.
Solution: Either modify the message, or change the check.