I'm not aware of any official guidance. My "rule of thumb" is that the statement of purpose should be adequate to allow a third party to trace proceeds; i.e. verify that the customer did what he said he was going to do with the money. Yours would seem adequate to that purpose.
For example, if you look at the account to which the proceeds check was deposited and see a check to a family member or several checks paying off miscellaneous bills with "family member's name" on the memo line you can conclude he did what he said he would do. If you one big check payable to a local Chevy dealership as a down payment, not so much.
It's an imperfect mechanism. In the short run, its value is dependent on a bank policy that requires proceeds checks either be payable to a third party or deposited to an on-us checking account.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.