I guess you can get rusty. Keeping my post above as a stark reminder that complacency can make you sloppy.
After a red-faced, "oh, god!" moment, I reminded myself of what the C-rating is compared to the CDR. The math works. These are (and this includes confirmed authentic VTC5'S) indeed true 30a
batteries.
On the upside, one point remains the same: These batteries should not be used at much below 0.2ohms. Too little headroom. A 0.5ohm coil offers 30% headroom. I strive for 25% or more.