Dr. Bilal Philips says that drawing lines in the masjid is an innovation. But when the scholars of the Standing Committee were asked:

What is the ruling on making lines on the mats or carpets in the mosques, because the Qibla is not square and with the building to help organize the rows; they replied, there is nothing wrong with that and if they pray without a line there is nothing wrong with that either, because the deviation from the Qibla doesn’t matter.”

Isn’t this issue based on intention, that is, one draws the line with the intention of making the lines straight?

Yes, you are correct. This is Dr. Bilal’s opinion on the matter, which he has taken from certain scholars. However, the more correct opinion on the matter is what you have mentioned, which is the opinion of the vast majority of Muslim scholars.

And Allah knows best.