My MCHN said its OK to pull them to standing, by just their arms, from around 5 months.
In fact she was surprised that I wasn't doing it.
She gave as a worsheet from the physio with exercises to do, and it was on there. You do need to be sure your baby is standing flat footed, i.e. with the whole foot on the ground, and obviously that he/she is ready for it.

With the jolly jumper, I think its more that they can bounce up and down on their toes only, which isn't conducive to optimal development.

Milo loves standing, being held by me, and 'bouncing with delight' he he thats what they call it in the developmental assessments!