the reason why i say, or i recommend learning on an acoustic guitar is because:

1. helps begginers with how to grip and hold chords
2. builds finger strength
3. bulids calices
4. it gets the begginer in to correct positioning of the right hand, as well as the handling of the guitar
5.helps with alternate picking for begginers as the distance between the strings is greater.

i do recommend it, but i wouldn't say it's the only way. i learnt on both, but i relied on my acoustic slighty more when learning chords and picking patterns