The primary reason why visual (under safelight conditions) development of radiographs should be avoided is:

The appearance of a developed but unfixed radiograph will be different in the dried state.

Removal of the film from the developer will affect the development time.

Film type and speed affect the appearance of images when exposed to a safelight.

Prolonged exposure to safelight can cause fogging of the radiographic film.

Visual assessment under safelight may lead to inconsistent development results.