I was thinking if American trucks crossing border from Syria to Iraq and back , are facing no great opposition by Iraq forces and it is safe for them , then why route not safe for Iran or Russia convoy to cross from Iraq to Syria now ? Instead of oil going to Syria then Lebanon ? Why is this not possible ? Who will target them ? American aircraft or Israeli ones or SDF or Rats ? I am talking about civilian trade and supplies and goods but also military hardware....
I think I got your point but you are treating crude and refined products as the same.
Syrian crude is shipped to locations where there are refineries, usually Turkey, Iraq and west Syria as well as a little processed locally. It cannot go direct to Lebanon as there are no refineries there.
Whilst the US, still the boss, will just about accept Egyptian gas via Jordan and Syria into Lebanon and some east Syria crude into Syrian Government territory I doubt they would go along with Syria processing and then exporting it to Lebanon, due to sanctions.