That dates the text to late 2nd or early 3rd century. And the heavenly witnesses reference has solid scholarship acceptance. For TNC, the “three witnesses” are not in Matthew 28:19.
No, your right "three witnesses" is not written in Matthew 28:19.
They are written here:
Deuteronomy 17:6 LXX
“upon two witnesses or upon three witnesses.”
ἐπὶ δυσὶν μάρτυσιν ἢ ἐπὶ τρισὶν μάρτυσιν ἀποθανεῗται ὁ ἀποθνῄσκων οὐκ ἀποθανεῗται ἐφ᾽ ἑνὶ μάρτυρι
Deuteronomy 17:6 Clementine Vulgate
in ore duorum aut trium testium peribit qui interficietur nemo occidatur uno contra se dicente testimonium
Deuteronomy 19:15 Vetus Latina (Sabatia 1751, Page 363)
In duobus teftibus aut in tribus morietur. Moriens non morietur in uno teſte.
Deuteronomy 19:15 LXX
“at the mouth of two and at the mouth of three witnesses.”
οὐκ ἐμμενεῗ μάρτυς εἷς μαρτυρῆσαι κατὰ ἀνθρώπου κατὰ πᾶσαν ἀδικίαν καὶ κατὰ πᾶν ἁμάρτημα καὶ κατὰ πᾶσαν ἁμαρτίαν ἣν ἂν ἁμάρτῃ ἐπὶ στόματος δύο μαρτύρων καὶ ἐπὶ στόματος τριῶν μαρτύρων σταθήσεται πᾶν ῥῆμα
Deuteronomy 19:15 Clementine Vulgate
non stabit testis unus contra aliquem quicquid illud peccati et facinoris fuerit sed in ore duorum aut trium testium stabit omne verbum
Deuteronomy 19:15 Vetus Latina (Sabatia 1751, Page 363)
Non manebit unus in teftificationem adversus hominem , fecundum omnem iniquitatem , et fecundum omne peccatum quodcunque peccatur : in ore duorum teftium aut trium ſtabit omnis fermo
Matthew 18:16
“at the mouth of two witnesses or three.”
ἐὰν δὲ μὴ ἀκούσῃ, παράλαβε μετὰ σοῦ ἔτι ἕνα ἢ δύο, ἵνα ἐπὶ στόματος δύο μαρτύρων ἢ τριῶν σταθῇ πᾶν ῥῆμα·
John 8:17
“because of the testimony of two men is true.”
καὶ ἐν τῷ νόμῳ δὲ τῷ ὑμετέρῳ γέγραπται ὅτι δύο ἀνθρώπων ἡ μαρτυρία ἀληθής ἐστιν.
2 Corinthians 13:1
“at the mouth of two and of three witnesses.”
Τρίτον τοῦτο ἔρχομαι πρὸς ὑμᾶς· ἐπὶ στόματος δύο μαρτύρων καὶ τριῶν σταθήσεται πᾶν ῥῆμα.
1 Timothy 5:19
“upon two or three witnesses.”
κατὰ πρεσβυτέρου κατηγορίαν μὴ παραδέχου, ἐκτὸς εἰ μὴ ἐπὶ δύο ἢ τριῶν μαρτύρων·
Hebrews 10:28
“upon two or three witnesses.”
ἀθετήσας τις νόμον Μωυσέως χωρὶς οἰκτιρμῶν ἐπὶ δυσὶν ἢ τρισὶν μάρτυσιν ἀποθνήσκει·
But a Latin translation of Deuteronomy 19:15 (Clause-B) "at the mouth of three witnesses" is quoted and is
eisegetically connected with Matthew 28:19 and Revelation 10:9's "three" letters etc.
The Comma's F+L+HS grammar is different to Pseudo-Cyprian's "Sermo de centesima, sexagesima, tricesima,".
Matthew 28:19's F+S+HS grammar is identical with Pseudo-Cyprian's "Sermo de centesima, sexagesima, tricesima,".
Pseudo-Cyprian of Carthage
"Sermo de centesima, sexagesima, tricesima," Edited by Reitzenstein, dans ZNTW, 1914.
Pages 86-87, Lines 348-352 (Modified slightly by me).
"lex enim Domini dura est et amara, [Line 349] <sed> amaritudinem facit, ut dulcedinem ostendat. nam et per Iohannem [Line 350] demonstravit, cum Spiritus [Page 87] librum angelo sigilla solventi traderet dicens: ”Accipe [Line 351] librum et devora eum et amaritudinem faciet ventri tuo, sed in ore tuo erit [Line 352] dulce, tamquam mel.” (Rev 10:9) hoc est per os trium testium probari, id est per os [Line 353] Patris et Filii et Spiritus Sancti confiteri, quod mel tribus litteris constat scribi; [Line 354] nam et mel quidem legimus tribus litteris statui.
"For the Law of the Lord is hard and bitter, but it makes bitterness, in order that it might reveal sweetness. Another example of this is shown through John, when the spirit hands over the book to the angel who broke the seals, saying: ”Take the book and eat it up. And it shall make thy belly bitter, but in thy mouth it shall be sweet as honey.” [Revelation 10:9] That is, "at the mouth of three witnesses," [Deuteronomy 19:15] this is to be established, which is through the mouth "of the Father and of the Son and of the Holy Spirit" [Matthew 28:19 (genitive case Latin)] it is to be confessed, because it is apparent that honey is written in three letters. For certainly, we also read honey, constituted of three letters."
No one-ness "these three are one", no "in heaven", no "there are three who", no "are giving witness", no "Logos", honestly - no Comma in view at all.
Your confirmation bias and obsession with the Comma, is leading you read the Comma into
a text that's obviously referencing Deuteronomy 19:15 (see the context of "the Law of the Lord" [Line 348]) and Matthew's genitive case "of the Father and of the Son and of the Holy Spirit".
You're very much mistaken.