Elon Musk has never been shy about expressing himself, especially about competitors. Lately, Musk has had some thoughts about Apple, especially as it relates to the iPhone makers' control over the apps you can install on your devices. That might seem curious since Apple, at least for now, isn't a direct competitor for Tesla. Then again, perhaps Musk is anxious about a day when that's no longer the case.

It started with the company's earnings call, when Musk talked about "walled gardens," and how Tesla was taking a different approach than other companies like, ahem, Apple. 

"I think we do want to emphasize that our goal is to support the advent of sustainable energy," Musk said about opening up Tesla's charging network to competitors. "It is not to create a walled garden and use that to bludgeon our competitors which is used by some companies."

Musk said that, and then fake coughed, followed by "Apple." 

The next shot came in a tweet, as it always does with Musk. A series of tweets, actually. Those came in response to someone who noticed that Musk seems preoccupied with Apple these days. 

It's worth mentioning that, in conversations I've had with people who would know, I get the distinct impression that Epic is interested in more than simply saving money on its App Store transactions. It didn't go through all of this trouble just to be able to use its own payment processor within Apple's App Store. Epic wants to be the App Store, at least for gaming. 

As for Musk, the shots themselves are certainly interesting, but more important is the reason Musk felt compelled to take them. It's hard not to notice that Musk's preoccupation with Apple comes as the latter seems to be poaching a considerable amount of talent from Tesla as it continues work on an electric vehicle of its own. 

That includes Doug Field, an Apple veteran who spent five years working as Tesla's Sr. VP of engineering before returning to head up Apple's self-driving car project. Field now reports to John Giannandrea, who heads up Apple's machine learning and artificial intelligence efforts after almost a decade of leading Google's search and AI teams. 

I mention it because, of any company that might have the ability to challenge Tesla, Apple is in a unique position. That's not to say that Tesla is in trouble, or that Apple will ever even release a self-driving car. I think Tesla will be just fine. It's not just the market leader when it comes to electric vehicles, its top-selling vehicles the Model Y and Model 3, sell more than all other EV makers combined.

At the same time, figuring out the problem of self-driving cars is clearly Tesla's top priority, and it turns out it's really hard. Musk even admitted as much recently, saying that it's a lot harder than he thought it would be. 

Apple, while not having any experience in building cars, is very good at figuring out difficult problems, and it has been busy hiring people who know how to do the car thing. That would make any business leader nervous, especially when you consider that Apple can afford to invest--for all practical purposes--limitless resources into what is still essentially a side project. 

But firing shots at your competitors isn't going to slow them down. It's also not going to detract from what they are doing. If Apple releases a self-driving car, people aren't going to ignore it because Musk tweeted the most common criticisms of the company. 

Instead, Musk might want to spend more time focusing on actually solving the problem. He's been promising full-self-driving vehicles for years. It's always just a few weeks, or few months away.