I agree with this, but out of curiosity, presumably the funds have their own blockers/SPVs below that they could just route their investments through and allow

I agree with this, but out of curiosity, presumably the funds have their own blockers/SPVs below that they could just route their investments through and allow other investors in the startup to receive the flow-through treatment (like we would in hedge/PE). My assumption was that the standardized governance structure of a Corp was also appealing to VCs who prefer it to the possibility of being screwed by an adverse amendment to the LLCA, etc.