"Even if banks conform to the ISO 20022 standard on messaging"
Hahahahahahahaha. These are banks, who suck in their breath through their teeth before they allow more than 80 characters per line, and think lower case is dangerously modern. They'd faint at the sight of ISO 20022. If you're lucky what they take is 'Standard 18', which is based on ANSI X 3.27 from 1978. Except that they don't even follow their own standard -- one bank insists you populate a specific unused field with zeroes, another requires you to leave off the "END" marker, and so on. And if you're unlucky they decide to roll their own format and end up with a CSV format with 86 columns, 78 of which you are required to leave blank.