Yes — in Jain philosophy, Jain Dharma is considered अनादि (beginningless) and eternal, so it is not seen as having a single historical “origin” like a created religion.

What Jain tradition says is:

• Jainism itself is eternal
• The Tirthankars appear in every time cycle to revive and teach the path
• In the current avasarpiṇī kāl, Lord Rishabhdev (Ādinath) is regarded as the first Tirthankar
• So, Rishabhdev is the first Tirthankar of this present time cycle, but not the “creator” of Jainism

So your understanding is partly correct:

• If you mean Jain Dharma is older than Lord Rishabhdev, then yes, in Jain view it is beginningless and eternal
• If you mean Rishabhdev was not the start of dharma itself, that is also consistent with Jain philosophy
• But within the current cycle, he is still honored as the first Tirthankar

In short: Jainism is eternal; Rishabhdev is the first Tirthankar of the present cycle, not the origin of Jain Dharma itself.