I take it that "account" is not the derived property in your example. I don't have any more insight into the answer than you, but look at this quote from the documentation:
"With that in place, when a Product is retrieved with something like Product.get(42), the SQL that is generated to support that will look something like this:
select product0_.id as id1_0_,
product0_.version as version1_0_, product0_.price as price1_0_, product0_.tax_rate as tax4_1_0_, product0_.PRICE * product0_.TAX_RATE as formula1_0_ from product product0_ where
Does this not clearly indicate that derived properties are keenly-loaded (or whatever the term is)?
If that is not sure enough for you, there is a logSql config option which you could switch on and check what is being generated.