If you don't have a persistence profile specified on the VIP, I don't think any persistence would be used unless specified in the rule. So no persistence should be used if the request doesn't match the /app/ clause.
You could test this by using your rule and making one request to /app/ and then a second request on the same TCP connection to a non-"/app/" URI. You can get a dump of the persistence table by running 'b persist all show all'.
If the persist command does take effect for the subsequent request on the same TCP connection, you could explicitly disable it by specifying 'persist none' in the else clause.
Aaron
Nimbostratus
