Gotta agree.
Hot tank is good for removing engine paint,dirt ,sludge,grease,oil etc but isn't particulary good at removing deposits in the block cooling passages and machine swarf,filings etc.
Hot tank really is only a passive clean up so the machinist has a clean engine to work on and repaint.Unless it is thoroughly cleaned up with pressure washing after machine work done and prior to assembly then there will be the above mentioned things still floating in cooling passages/oil passages.I've seen the results many times of failed engines years ago when I was on the spanners from so called professional engine reconditioners that should have been more professional and taken better efforts to thouroughly clean up an engine before assembly.
Thats why I say the only way to completely flush out the shit within an older engines cooling passges is to remove all welch plugs and pressure wash the crap out.