Question about the Canon R5

[escoutdril54]

So I realize there probably aren't many engineers lurking here but hopefully some of the more technically proficient people can answer my question.

If the Canon R5 has the capability to shoot 8K RAW, why can't it shoot 4K RAW? As of right now, the spec sheet lists 4K to be only available with ALL-I. ALL-I, 10bit, 4:2:2, is good enough for me, I'm just curious what the technical roadblock is for shooting 4K RAW.

Thanks in advance.usps tracking showbox speed test