ATA_STATIC_ID and AHCI bug or /dev/hands ?

Hello!

I found some odd behavior of  ata device numbering. It seems, that there
is no effect of option ATA_STATIC_ID in CURRENT.
What I have:
supermicro server with 4 sata ports onto Intel ICH7 SATA300 controller
recent CURRENT
sata mode in BIOS is Enhanced
ahci support in BIOS in Enabled
option ATA_STATIC_ID in KERNCONF

So, if I boot with 4 HDD connected to sata i found ad4,ad6,ad8,ad10 as
disks. but when I detach disk, which "was" ad8 in last case, and then
reboot - I see ad4,ad6,ad8! and not ad4,ad6,ad10! atacontrol list
doesn't show an empty ata channel. Only channels with HDDs connected. I
check 6.x 7.x on the same server with _the same configuration in bios_ -
and all works as suspected - there are empty ata channels, there are
really static device numbers. when I set AHCI to Disabled I have just
two ata channels (with AHCI - I have four, one for each sata disk) and
with or without HDDs connected I see empty channels and have really
static dev nums in the same CURRENT.
So my question is - is it my fault? does I miss something? Or it is a bug?

Yes ;) I know about glabel, but my setup is complicated enough without
them ( gpart-ed disks with zfs-only setup) so I do not want to make it
more complicated.
And with such behavior  I cannot  add  disks  on  the fly, if there is
no empty ata channels.

--
    With best regards,
    AVR39-RIPE