That’s a really god question, kudos for asking that!
The answer is that you have to no reason to do so, and you shouldn’t do it! Luckily you don’t have to, MCSBackup is built upon the shoulders of trustworthy giants such as Linux, OpenZFS and RSync. Which for decades have been used and trusted in all corners of the IT Industry.
On top of the MCSBackup itself is open source, so you can sit down and read through the source code – and that way you are able to verify exactly what is being done and how. If you do not have the necessary competences to do this you can always hire a professional company to provide commercial support, and through that way get a support agreement which you can trust with all the powers of the local courts and legal system.