Yes sorry you are correct A6 is not a CFT but A5 is a CFT/WW and only had a value of 216,959cr offered for it. I wonder if they have removed the terraform bonus if the planet has already been discovered?
I'm pretty sure that it's just that the terrarforming bonus has that pesky multiplier we can't nail down. You've hit some zeroes, or close to, but that's not unexpected. The values in EDSM and EDD are estimates, not guarantees, and with CFTs the difference can be large. It is what it is.