Sammy, imho 'all tube' means that all signal processing is in the tube domain...preamp, power amp and all on-board effects. IMe, this is how most techs look at amplification methods.
None of those Kustom amps is all-tube. In fact, many modern amps that are purported to be 'all tube' are not in fact all-tube amps. Fender Hot Rod and Blues Deluxe/Devilles are not all tube in that the reverb is in the solid state domain. Peavy Classic 30's and 50's are the same way. Many of the big Marshalls process the reverb in the solid state domain. JCM 900 Dual REverbs process not just the reverb but much of the gain stages in the solid state domain. I find it informative to soem extent to count the number of preamp tubes. IF an amp does reverb and some extra gain but only has one tube, it is in effect a hybrid amp to some extent. IF it does reverb and gain but has 3 12A_7 tubes, it is qeustionable that it is all-tube.
LOok at a vintage Fender REverb amp. IF you did away with the Normal channel;, you could do away with one 12AX7. You would still have 5 12A_7's in the amp...and there is no hi-gain going on. It takes 5 12A_7's to do the preamp, the reverb, the vibrato and the PI in that single channel, non-switching gain type of scheme.
this 'all-tube' hype or simply 'tube amp' thing from manufacturers is much like the Class A hype....it usually isn't a case of the 'truth, nothing but the truth' type of claim. Buyer beware, right? That is, beware if all-tube makes any difference to you. I hear that SS reverb.