He's also drinking brown on the zeppelin, though perhaps not the sort of Scotch he tried in the Bantam novels. (Pity that Dance of the Giants doesn't take place on Islay; it possible that the famed digger doesn't like his liquor to taste too much like his work?)
***
All right, detour into a non-Raiders source.
Actually, I've found at least one relevant line from <I>...Dance of the Giants</I> at Google Books. Seems like a conditional, not categorical, dislike of the stuff.
A waiter arrived and poured Indy and Deirdre shots of a local brand of Scotch. Indy took too big of a swallow and felt it burning all the way down to his stomach. He coughed into his hand.
"A good batch, don't you think, Professor Jones?" the mayor said, holding up his glass.
"Great." He felt like fanning his mouth.
***
And now here's the August 1979 Raiders draft's version of the despairing Indy scene, suggesting Pale Horse has it on the money.
A dark, smoke-filled den on iniquity. The patrons, almost all
fearsome Arabs, sit in small shadowy groups around the room.
Indy stands at the bar finishing off a fifth of bourbon. He
is drunk. The ARAB BARTENDER places a new bottle of expensive
bourbon in front of him.
Does this mystery bourbon have a name?
Yes, it does!
That's Belle of Lincoln Straight Whiskey, from the Jack Daniel's distillery.
Now, if I felt like digging into the accuracy of this, I might note that Jack Daniel's wasn't producing anything in 1936, due to the national prohibition and an earlier one in the state of Tennessee. I might also note that Belle of Lincoln was
an older label, perhaps no later than 1912, and that it was shaped just like an ordinary Jack Daniel's bottle, square edges and all.
Maybe
the revival of the Belle of Lincoln brand in a limited 1979 run of decanters (looking neither like Indy's bottle nor the familiar square-bottomed bottle) is what put the Raiders prop team on the label's scent.
If we're looking for an in-universe explanation? American bootleg liquor put in an unrelated bottle with a genuine-looking label slapped on the front might do. Because before there started being fan replicas, I think the bottle Ford handled on set was the <I>only</I> Belle of Lincoln whiskey bottle that looked just like that.