Klaus Ford wrote the anda grading standard. It should come as a surprise to noone that the effect of cleaning on a coin isn't mentioned in that standard.
Firstly, I would say that ANDA is a group that exists to support its members - namely dealers, not the wider numismatic community.
Secondly, on the issue of cleaning, while I understand that many may view it to be ethically dubious, we do need to bear in mind ancient coins, and the re-sale of coins that have previously been cleaned.
Note: in stating that, none of the above changes my personal view that the use of silver dip (in an attempt to increase the sale value of a coin) by a dealer is unethical.