For some toddlers pull ups can hinder potty training while for others pull ups can help potty training.
Pull Ups can feel like diapers because in reality pull ups are just pull on style diapers although they are less absorbent.
If a toddler is wearing pull ups and pees in them then they won't feel wet like they would when wearing underwear.
Just like a diaper the pull up absorbs the pee and so the toddler does not feel wet.
But if the toddler is wearing underwear then they will feel the wetness on their underwear which makes them feel uncomfortable and so they would want to use the toilet.
However some kids do potty train just fine with pull ups and they are good for when away from home to catch any pee or poop.
At home though its best to keep the toddler in underwear.