No, it is not true!

Iqbal's interest in Khushal Baba's work grew after he came to know about him through Raverty's translations. He then sought help in translating Khushal's poetry and wrote extensively about him in prose & in poetry.

He even asked the Afghan education https://twitter.com/Azmatalli/status/1252533445894569984

minister to initiate a scholarly study of Khushal's great poetic work to tap the greatness and value that was there in Khushal Khan Baba's work for the benefit of the Afghans.

If I'm not wrong Iqbal introduced the Urdu & Persian speaking world to the works of Khushal Khan Baba.

You don't do such things if you're copying or plagiarizing someone's work. It is unfortunate, and at the same time disgusting, that certain people who are filled with hatred peddle these lies through their propaganda networks.

Why do they do it?

They've not read Iqbal, and missed out on the explicit & implicit 'adaptation' mentioned in Iqbal's work.

Or, they're reacting/protesting that Iqbal gets more attention than the Pashtun's scholars & poets.

Or could it also be that they're opposed to the Iqbal's idea of 'Umma' based in religion of Islam that rejects ethnic-nationalism in the first place.

Otherwise, how can one ignore Iqbal's praise of Ahmad Shah Abdali, Jamal Ud Din Afghani, Amanullah Khan, Nadir Shah etc,.