In India the ‘pillion’ rides a two-wheeler on side-saddle due to the clothes worn. In two-wheeler physics, this is a bad idea. Side-saddle riding allows a rider to sit aside. Astride is when a rider keeps legs on both sides of the two-wheeler.
Neither the rider nor the pillion just ‘sit on’ a two-wheeler. They use legs to grip the bike to hold themselves, along with pressure on the foot pegs and the weight of their bum on the seat. When riding side-saddle, the pillion loses the ability to use legs and feet to steady, prone to accidental fall.
Sections 128 & 129 of the MV Act 1988 talk of pillion riders, but are silent on the posture i.e., side-saddle / astride. If the silence of law were to be interpreted for public safety, then there is no death / disability benefit to any side-saddle pillion rider. The Indian insurers are generous!