It bears on his bad theology, which is the subject of a sub-discussion, which you are not a part of.
I'm not sure where in Hebrews you can find anything that would contradict GGG. However, many Christians(if not the vast majority) believe along the lines of the Nicene Creed. Anyway, my King James version of the Bible states Hebrews 1:2,5,8-10 thusly.
Hbr 1:2 Hath in these last days spoken unto us by [his] Son, whom he hath appointed heir of all things, by whom also he made the worlds;
Hbr 1:5 For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
Hbr 1:8 But unto the Son [he saith], Thy throne, O God, [is] for ever and ever: a sceptre of righteousness [is] the sceptre of thy kingdom.
Hbr 1:9 Thou hast loved righteousness, and hated iniquity; therefore God, [even] thy God, hath anointed thee with the oil of gladness above thy fellows.
Hbr 1:10 And, Thou, Lord, in the beginning hast laid the foundation of the earth; and the heavens are the works of thine hands: