you do realize that a hot tank is just a cabinet w/ a turn table, water jets, a water heater and a resivoir full of some solution... its not infallible and it doesnt get into EVERY nook and cranny... im sure you wouldnt be able to pop out your freeze plugs and clean inside your water jacket PERSONALLY.

you have maybe a 1.5" hole to work thru at the most... how Good of a job could you possibly do?

btw, degreaser solution doesnt reverse years and years of corrosion caused by neglected cooling systems/coolant. thats why professional cooling system flushes are for; they remove scale, corrossion and buildup.

a hot tank degreases and de-dirts the block. im sure it did its job just fine.

also, im sure they wanted to hot tank your block because it still was dirty and had oil and stuff on it. they dont machine or even work on any motor unless its "Spotless". if you go in the back and touch any part in the "Clean" part of the shop, itll be just that; Clean.