Research
Height has several uses
Logs, shrubs, trees, posts and similar structures can provide basking exposure, a view of the surrounding area and separation from some ground-level threats. Height also changes wind, shade and radiant heat.
The animal is not choosing a structure for only one reason. The same elevated position can support observation, temperature control and security.
Research
Ground and shelter still matter
Open ground is used for movement, foraging and direct sun exposure, while vegetation, crevices and burrows provide retreat opportunities. The useful habitat is the relationship between these features, not any single object.
This helps explain why a photograph of one wild dragon on sand, rock or a branch cannot by itself prove that the species needs only that surface or structure.