Hmmm sehr merkwürdig das alles und nein Adresse 1PYmLWu59GpTJctSZDo7KVaUJyu8pWn4Vu ist nicht meine bzw gehört auch nicht zu mir, da ich nur noch native Segwit Adressen habe 
Das liegt vermutlich daran, dass es für das Signieren von P2SH (nested SegWit, 3xxx) / und bech32 (nativem SegWit, bc1qxxx) noch keinen einheitlichen Standard zum Signieren gibt. Daher können solche z.B. in Electrum signierten Adressen auch nur in Electrum verifiziert werden, weil Electrum das von sich aus implementiert hat. Zudem schreibt achow101 (Bitcoin Dev) folgendes:
My doubt, regarding signing in segwit address is if this is a "bug" and will soon be corrected, or is it an abandoned feature?
It is neither a bug nor an abandoned feature. It is just that we are still working on creating a more generalized signing scheme that lets people sign with things like P2SH addresses (e.g. sign with a multisig address). There is simply no standard yet for signing with such scripts or with Segwit.Note that you don't actually sign with an address. You sign with a public-private keypair and your wallet interprets it as an address. Your wallet could just as easily interpret it as a segwit address. We are working on creating something that actually specifies the address type, and more generally, allows signing with scripts.
Und weiter:
And paste to https://brainwalletx.github.io/#verify
It'll automatically recognize the legacy address used for that signed message.
Because either way, the message was verified using the address: 1NtMnD5BQrRvVeHDk4HXaGvXiVkUuTjhXf, not bc1q7qgn8zw75n26hd60a8ay42482mukdjrdv3cyp7.
But both can be derived from the same prv key, so there wont be a serious problem with future verification.
The only difference is: those extra steps are some kind of proof that the result legacy address was based from your SegWit address.
It'll automatically recognize the legacy address used for that signed message.
Because either way, the message was verified using the address: 1NtMnD5BQrRvVeHDk4HXaGvXiVkUuTjhXf, not bc1q7qgn8zw75n26hd60a8ay42482mukdjrdv3cyp7.
But both can be derived from the same prv key, so there wont be a serious problem with future verification.
The only difference is: those extra steps are some kind of proof that the result legacy address was based from your SegWit address.