I never take anything manufactured for granted. The only near-perfectly illuminated and true 5000K at the surface light box I've ever seen is the one I modified myself, or essentially rebuilt entirely. Only the outside housing and sockets of the original remained. This relies upon true 98CRI color matching tubes.
Equivalent LED strips have to be ganged together and well diffused to work in this manner. There is a patented kind in which the blue elements are overlaid with violet filters to truncate any cyan bias in these. You can't just buy a bulb. Expect to spend hundreds of dollars for the correct LED strips alone, plus a dedicated power converter. I'm speaking of course about high-end color evaluation or top quality copy lighting. For just casual applications like web work, there are cheaper options. But there too, you get what you pay for. If the price seems to good to be true, something will indeed be way off.
Very few light boxes rated this or that even bother to take into account secondary variables which affect the final output. Once you pull out an actual color temp meter, it's like walking into a cave filled with cobwebs and bat droppings. Truth in labeling diminishes in direct proportion to the degree something is considered an amateur bargain product versus a professional item.