There is a regulation calling for wiring accessories to be suitable
for their environment & likely usage. Indeed, 300mm is the common
figure from the sink - not necessarily the strainer. The same 300mm
from a hob re trailing cables.

No limitation under a sink, although TBH I would prefer a simple
splashproof enclosure (you can buy them, clear or transparent that
take a standard wiring accessory allowing cheaper flexibility than say
Masterseal).