APK safe to download? ToS?

The Update already got rolled out. You just Need to wait some hours

The apk is the update...if you mean is it against the ToS to source the apk from 'apkmirror' or another site then the answer is... 'no, it isn't against the ToS'

I believe they cannot detect IF the APK you downloaded is from a reputable site like apkmirror.com since it has the same digital signatures etc. Basically, you're downloading the same update rolled first. You're simply sideloading the apk. From where I am, updates tend to be delayed so I rely on apkmirror for huge updates. If any normal ones roll out, PlayStore recognizes it has the same digital signature so I don't have any issue updating inside PlayStore itself. For me, the real danger would be to download from a questionable site since some of them modify apks and such.