This is news to me. I've always believed that only CDTV, A570, and CD32 could boot directly from a CD alone. It would be great to find out I was wrrong. Grin.
I've heard that polling the SCSI CD drive can take longer depending if there is a CD in the drive, on some setups. Maybe you could boot with and without a CD and time it both ways.
Is your 3000 accelerated or a stock 68030?
If you try Thomas' suggestion, I hope you post the results. I'm curious about this, too.