Think about the interaction you'd be causing.
Customer wants to report bug, doesn't know what complaint checkmark does => will check because he thinks it gets resolved quicker.
Customer has checked bug as complaint, has expectation that complaint is addressed as such leaving you no initiative.
Looking at it from the standards side, I like ISO 13485's approach which considers a communication to be an alleged deficiency (with some specific characteristics to check). Then there is the determination whether it actually is (customer's claim might be disproven using company or complaint information), e.g. it's not a non-conformity as it doesn't relate to a claimed or implied specification towards customer nor an internal specification. Thus in my mind complaint handling was always the transformation from alleged (complaint) to true (non-conformity; now to decide what to do towards customer and towards the (design) problem) or false (disproven allegation;might still be opportunity for improvement/development) based on complaint investigation.
The ISO 9000 approach uses "expression of" and "explicit or implicit expectation", which makes it a bit too vague. I do appreciate that it covers the interaction process itself as worthy of being targeted by complaints.
Source definitions (from ISO OBP).
complaint (General)
<customer satisfaction> expression of dissatisfaction made to an organization (3.2.1), related to its product (3.7.6) or service (3.7.7), or the complaints-handling process (3.4.1) itself, where a response or resolution is explicitly or implicitly expected
ISO 9000:2015(en), 3.9.3
complaint (Medical Device Industry)
written, electronic or oral communication that alleges deficiencies related to the identity, quality, durability, reliability, usability, safety or performance of a medical device that has been released from the organization’s control or related to a service that affects the performance of such medical devices
ISO 13485:2016(en), 3.4