also a rope tied on him, so if the high priest was struck dead, they would know because the bells stopped jingling, and they could pull him out, because anyone who went in to get the body would also be struck dead, because absolutely no one was to enter the holy place except the high priest, once a year, on Yom Kippur.
but Christ entered the true holy place in heaven and put His own blood on the true altar -- and the veil was rent.
i think Eusebius wrote hyperbolically -- maybe inspired by this:
Therefore, brothers and sisters, since we have confidence to enter the Most Holy Place by the blood of Jesus, by a new and living way opened for us through the curtain, that is, His body, and since we have a great priest over the house of God, let us draw near to God with a sincere heart and with the full assurance that faith brings, having our hearts sprinkled to cleanse us from a guilty conscience and having our bodies washed with pure water. Let us hold unswervingly to the hope we profess, for He who promised is faithful.
(Hebrews 10:19-23)
this isn't speaking about the literal holy of holies in the temple, but it is speaking spiritually of heavenly things.
and just think about this realistically for a moment:
James had become a believer in Christ. the Jews still controlled the temple and Jerusalem ((so much as possible, under Roman occupation)). the church in Jerusalem was heavily persecuted -- hence the collection Paul took up from all the churches scattered around the Mediterranean, to help the believers in Jerusalem.
does it really seem likely that the Pharisees and the Sanhedrin allowed a non-Levite, Christian believer - who they considered a blasphemer worthy of death - to regularly go into the holy of holies? because he was a 'pretty good fella' ?
or is it more likely that what Eusebius wrote about James is an hyperbolic statement, with reference to Hebrews 10, about James faithfully interceding in prayer? entering a spiritual 'holy of holies' to meet with God in prayer, able to do so now by the blood of Christ?