Default TWRP Nandroid restore - kernel ?!

When restoring a Nandroid backup in TWRP, selecting only the "system" and "data" partitions, does it not also restore the previous kernel ?!
In others words, isn't the kernel stored in the "system" partition?

I just restored one, "system" and "data", and was surprised to find that the kernel I flashed after I took the backup is still present...
Samsung Galaxy S3 i747m 32Gb + 64Gb ext. SD
Stock TW Kit Kat 4.4.2 + root + Xposed + Wanam
Daily driver phone
Samsung Galaxy S i9000m 16Gb + 16Gb ext. SD
Slim Kat & Semaphore JB kernel
Backup & flash addiction relief phone