now your front end server(litespeed) is able to serve both http and https, and between the front end and backend server, has established http connections only and works.
https ssl connection has extra overhead than http. usually backend server is not open to public, so http is preferred.
while https connection with backend server looks possible, it's not necessary in most cases.
pass https directly to backend server, is more a load balance feature, which litespeed load balance(lslb) may support it in the near feature(layer 4 load balance)