Actually it’s more like buying Lawn Mower A, which actually is as powerful as Lawn Mower B, but which has firmware that prevents it somehow from cutting grass of a certain height for “power efficiency reasons” (in other words, so the company can get you to buy two lawn mowers instead).
So no, not at all like asking a lawn mower to have wings.
It's more like this: Lawn Mower A... has no air intakes or engine cooling fans, is less width than Lawn Mower B, has a thinner chassis than Lawn Mower B with all of its internal sandwiched together, has a smaller fuel tank than Lawn Mower B, Lawn Mower A also has to be held with two hands and floated over the lawn to cut it as it has no wheels and is not self-propelled. Lawn Mower A is meant to be as portable as possible and Lawn Mower B is focused on more power output and better productivity. Lawn Mower B is wider than Lawn Mower A, Lawn Mower B has wheels and air intakes along with cooling fans, it is self-propelled, has a relatively large fuel tank, and has a thicker chassis with its core internal components separated from certain engine components for better cooling.
While the engine is the same/similar, Lawn Mower B is faster at cutting grass because its cutting swath is wider, it’s self-propelled, and its sustained power output is higher than Lawn Mower A as it has better thermals for cooling. Lawn Mower A throttles and limits its sustained power output more because it doesn't have the thermals to support the kind of sustained power output compared to Lawn Mower B. Furthermore, with less power output, that causes the speed of the cutting blade to be slower, causing the cutting to be slower.
Lawn Mower A will never be the same as Lawn Mower B, and vice versa. They are distinctly designed and the design of Lawn Mower A necessarily limits what its power output is. And even if it could have the same power output, its missing key things that Lawn Mower B has...
The iPad is a thin slab of glass, that's it. The MacBook is two pieces: a relatively large screen and a bottom base where all of the internals are along with a physical keyboard. The bottom base provides a large foundation for a heat sink and fans and for that heat to be radiated in multiple directions to dissipate. The iPad has all of its internals sandwiched against the screen in what must be a very thin package by design as it's a tablet first that needs to be held in the hands for longer periods of time.
Size matters, in many respects, and that includes screen by necessity. The smaller the screen, the less precise desktop interfaces make sense. That means macOS makes no sense on an iPhone: the screen is too small. macOS makes no sense on the iPad Mini: the screen is too small. macOS makes little sense on the 11" iPad Pro or iPad Air: the screen is too small. macOS could work on the 13" iPad Pro in terms of screen size, but then you are stuck with a tablet design, and the thermals and its screen's aspect ratio and all of the thermal issues, reduced battery size, etc. come into play.
On the software front, macOS provides for better productivity due to things like much more information that can be presented per square inch of screen because of precision inputs and screen size: e.g., contextual menus in software applications, tool palettes with many options in a small area, etc. It's more efficient to interact with. Yes, you can get a MKB with the iPad, but you're still going to be stuck with a smaller screen, less precision input... all leading to reduced productivity/reducing the amount of information that can be displayed on screen.
The iPad is distinct as a tablet first, and for good reason. The MacBooks are distinct as laptops, and for good reason.