If you read the fine print, those offering data recovery on iPhone 6 models or newer will have the caveat that the device must be still bootable, and you must remember your passcode. Basically all they can do is provide a workaround for a broken or unresponsive display. As long as everything other than the screen & input is working, and you have not forgotten your passcode (so the encryption system and secure enclave are still accessible for you) they may be able to pull some data. Even under these every restricted circumstances, they won't be able to recover everything.
And if your device has already gone into recovery mode, even knowing your passcode won't help, as the encryption is now permanently locked in, with no longer any means to decrypt it.
Any one of these companies though will happily take your money, claim to try to recover data for you, only to report that they were unsuccessful. They all have plenty of legal fine print to obsolve themselves of any responsibility when their software fails to provide you with any actually useful service.
These publically available, commercial software recovery tools are simply outgrowths of old, old technology to recover data from unencrypted drives and storage that got reformatted. They cannot deal with encrypted data, especially data from a complex synergistic hardware/firmware and operating system encrypted scheme like that used in current iOS devices.
Quite bluntly, even when successful in recovering non-overwritten data on a simple reformatted storage device, these commercial tools offer nothing more than other, open source Linux (and even, back in its day, MS-DOS) tools have offered for decades. They count in the fact that most people are not familiar with, or don't wish to learn to use open source data recovery tools run from a Linux or other boot device, or gullibly believe that these companies can magically crack strong encryption systems.
