Yeap, and I think the term should be used to determine what you refer to as on-chain transaction volume.

As I know, other on-chain analytic website does offer to show the transfer volume data, like Glassnode for example. I suggest you can compare between the number calculated by the tool with other trusted on-chain analytical sites. As an example, you can see a successful on-chain transfer volume of USDT on Glassnode, the number shows ~3.8B USD on 20th November. You can see it here. I think it might be helpful if you compare what those sites number tells and with what your tool show, it would help to test whether the number on the tools given is probable or not.

Just a side note, I think altcoin boards are having a lack of technical discussion or solutions, specifically about some of your issues, unfortunately, others may find it hard to help you, so do I since I didn't have experience playing around with web3 yet.