If he gobbles after eleven, he is going to heaven.
Good theory. My personal experience is a bit different, though. I hunt primarily Merriam's turkeys, which are admittedly notoriously more inclined to gobble when prompted. Here's my theory on the birds around here.
If he gobbles once, he may just be giving you a "courtesy" gobble. You can pull those gobbles out of a bird with some regularity, but it doesn't necessarily mean anything in terms of whether he is going for a ride in the truck later. There are lots of gobblers around here that will give you that single "I am letting you know I am over here" gobble,...and quite often, that will be the last time you hear from them.
Now, if you can get him to gobble a second time, your odds have definitely gone up, but nothing is conclusive yet. But that does give you a clue that he is at least interested in having a conversation with you. However, if he is closer on that second gobble, things are a bit more promising for a face-to-face discussion. ...But not always.
For me, it is that third gobble that is usually the clincher. If he gobbles three or more times,...and in addition is closing the gap,...I am mentally cooking up turkey nuggets at that point. He is likely to be having his snood flopping in the dirt in short order.
Of course, there are variations on the theme above, but it is consistent enough that I have confidence in starting to heat up the cooking oil after that third gobble!