How Spring deserializes query params into Kotlin data classes?

Assume a Spring @RestController with a simple @GetMapping that accepts a VenueQuery dataclass as its parameter:

data class VenueQuery(
    val cityId: Long? = null,
    val countryIso: String? = null,
)

@RestController
open class VenueController {

    @GetMapping("/venues")
    open fun getVenues(
        request: HttpServletRequest,
        response: HttpServletResponse,
        venueQuery: VenueQuery
    ) { ... }
}

Runing the code as above, works "well". GET /venues?cityId=1&countryIso=CZ gets deserialised into VenueQuery(cityId=1, countryIso="CZ"}.

However, annotating the venueQuery function argument with @RequestParam causes the same request to be rejected with BAD_REQUEST "Missing required parameter 'venueQuery'". This makes sense, but renders the former case even more confusing.

After searching for quite some time I still can't answer the following questions:

1. Where can I find a documentation that describes this behavior in more detail? I.e. any reference I could point to instead of relying on a one-time observation?
2. Is the first case even an expected behavior?
3. How does spring knows it should populate the venueQuery argument with query params, but not the request and response params? Does it infer by its types of servlet request/response?
4. Generally I struggle to find any documentation (not a "how to" but documentation) about how the Spring annotations and principles apply in Kotlin. Are there any notable sources?

Thanks for any answers!