No, that's not a correct statement. The indirect costs may not be specifically for a specific Surface unit, but the Surface division does have indirect costs that are specifically its own costs. This means that there are, indeed, indirect costs that are specifically Surface's. The Surface factory pays rent, taxes, electricity and utility. These are all indirect costs, and they are all specifically for Surface.
And parts of the general overhead should also reasonably be allocated to that line, if you run a Surface ad that should probably be specific indirect cost but if you have a stand at a conference promoting all your products then a fraction of that cost should probably be considered Surface marketing costs. All companies do some form of internal cost assignment that is more detailed than what the official accounting practices gives you but since they're easy to manipulate they won't show them to investors as you could easily be sued over giving a false impression of the profitability of one particular product or service.
What's worse when it comes to investment decisions is that even if the costs are properly allocated - a very big topic in itself, particular for example what costs employee time, equipment time, equipment wear, storage or use of consumables instead of direct expenses - is that cutting one product line won't necessarily cut the allocated costs. A textbook example is a chicken farm where you sell chickens breasts, legs and wings. Even if you find out the wings aren't profitable through the cost allocation, it's pretty hard to make chickens with no wings so dropping the product wouldn't actually cut the costs, just force a re-allocation.
Another fun part of this is the impact dropping some products or services can have on others, for example say you run a grocery store and find that selling milk is really making you no money all, in fact you're losing a bit. But if you tried to cut milk from the store, you'd find a lot of customers start shopping elsewhere. It's amazing how many companies have fallen into this trap by cutting auxiliary non-profitable products only to find they were necessary to make the profitable sales. Or in other areas like public transportation, if they cut the off-hour lines people buy a car and use that instead of the bus altogether.
It's not all bean counting 101, like in tech there actually are complex interrelations in business too. Most of it isn't rocket science but if you use too simplistic models it might fall flat on its face in reality. The GAAP figures they publish for the stock market are not made for detail, they're made for being correct and comparable which highly limit their depth because they don't want to give companies the degrees of freedom to manipulate the numbers. Trying to accurately say how a small product is really doing in a big company's books is actually very, very hard.