If spinal nerve roots exit above in the cervical region and below in the thoracic and lumbar region, would a disc bulge that is posterolateral at L4-L5 affect the L4 nerve root or L5? And why?

In general, nerve roots are named after the vertebra above them. For example, the nerve root that exits between the T4 and T5 vertebrae is T4. However, the cervical nerves are different. Although there are only 7 cervical vertebrae, there are 8 cervical nerves, the first of which exits above the first cervical vertebra. So in the cervical spine, the nerves are labeled after the vertebrae below them e.g. if C5 – C6 vertebrae are highlighted, then the nerve root that passes between them is C6. In order to be clear, it’s usually best to specify nerve roots by referencing both vertebrae. [1]

My attention has been drawn to a supposed L4/L5 exception (i.e. L5 nerve root exiting between L4 and L5 vertebrae instead of L4 nerve root as explained above). However, my review of current literature does not provide any evidence to support this exception. The L4  nerve root buds off the thecal sac at the mid L4 vertebral body level and after rounding the pedicles, it leaves the spine through the L4 neuroforamina between the L4 and L5 vertebrae. [2]

Reference 1, Reference 2