Does not hurt to start diesel without glowplugs... IF it will start it just means you have good compression, good starter and battery, good fuel dispersion...
ONLY if you are having start problems ... typically when the engine is cold... then the glowplugs really are important.
Thank you jt20... exactly correct.
Some people may be hearing the timing circuit for the light go off... Etc... which is only a ' suggestion ' type device... use a watch to time the glow... people typically can not guess at time well...