>>19645397No, アラン can be interpreted as both Alan and Alain, however, we never saw アラン written as "Alan" in any official material, Serebii/Bulbapedo only assumed that it was Alan because it is a more common name than Alain.
When the dub came out and revealed that his name was Alain (because Alain is Alan in French), it makes sense that his name was Alain the whole time and never actually Alan, the latter name being an assumption that turned out to be incorrect.
Both names are interchangeable but if you want to be technical, Alain is right.