Why the symbol BRL/BUSD doesn't exist, but the symbol BUSD/BRL exists?

Let’s assume that I want to buy, for example, symbol BRL/BUSD in my application (buy BRLs paying with BUSDs). When I execute a query I get an error, because there is no symbol BRL/BUSD, but the symbol BUSD/BRL exists. So I can use symbol BUSD/BRL to achieve my goal. In another words, I need to execute the second query!
To buy BRL using BUSD I need to make two queries to the API - the first one to understand, that symbol BRL/BUSD doesn’t exist, and the second one to use BUSD/BRL instead.
The question is how to make this in one query? How can I optimize this?

P.S.: I took BRL/BUSD just for example. This problem is really common and you can see the same thing with many other symbols.

“BUSDBRL” is available, but not BRLBUSD, so you can buy BUSD with BRL or sell BUSD for BRL.