In addition to other arguments, if one makes 3 sets of words from KJV text:
Set 1 includes all the words that appear in the Bible between Genesis through Acts plus those in James through Revelation. These words are Bible words used by the various Bible authors. For the moment leave Paul's writings and the author of Hebrews out of consideration.
Set 2 include all the words that appear in Romans through Philemon. These are the words of Paul and may also include many of the words that also appear in set 1.
Set 3. All the words that appear in Hebrews. These are the words that were used by the author of Hebrews.
What words appear in set 2 that are not in set 1?
These are words that only Paul used.
See Paul's Exclusive Words in Rom-Phm (searchable links for words)
Which of these words also appear in set 3?
These are words that only Paul used and are also used in Hebrews.
(but nowhere else).
See Paul's Exclusive Words that are in Hebrews also (searchable links for words)
Paul's Exclusive Words Used in Hebrews 1.0
Did Paul write Hebrews?