It's clear, from watching Russia fail to be completely sanctioned that this is not watertight. The question I have is: have these sanctions added a money laundering tax to doing business? How much? What is the cost of enforcing the sanctions vs the added cost and is that worth it?
I don't know if this has been explored, bit I think it's an interesting follow on to "all or nothing" watertight sanctions.
Yes, that's pretty much the main goal with sanctions (and things like export controls): no-one expects them to be impossible to work around, but they should impose some (ideally very large) extra costs and limit the scale. For some things this is more or less built into the regulations with de-minimis rules that tacitly cap the cost multiplier at 10x or so.