Also, SafetyNet is deprecated, and Google has said that app developers shouldn’t use it for a long time before that, so I’ve never had to use it. My experience of a blob-free microG has been really good, and I trust FOSS code a hell of a lot more than sandboxed proprietary code, because I can’t be sure what it does with the data I inevitably do provide it.
MicroG has also been very clear IMO about SafetyNet not being a reimplementation, but rather a sandbox when it was relevant.