All of that "plumbing" affects behavior. My argument is that all of the brain energy used when checking that behavior is necessary in order to check that behavior. Do you have a test for an off by one error? Do you have a test to make sure your counter behaves correctly when there are multiple components on the same page? Do you have a test to make sure errors don't cause the component to crash? Do you have a test to ensure non utf-8 text or binary data in a text input throws a validation error? Etc etc. If you're checking all the details for correct behavior, the effort involved converges to roughly the same thing.
If you're not checking all of that plumbing, you don't know whether or not the behavior is correct. And the level of abstraction used when working with agents and LLMs is not the same as when working with a higher level language, because LLMs make no guarantees about the correspondence between input and output. Compilers and programming languages are meticulously designed to ensure that output is exactly what is specified. There are bugs and edge cases in compilers and quirks based on different hardware, so it's not always 100% perfect, but it's 99.9999% perfect.
When you use an LLM, you have no guarantees about what it's doing, and in a way that's categorically different than not knowing what a compiler does. Very few people know all of the steps that break down `console.log("hello world")` into the electrical signals that get sent to the pixels on a screen on a modern OS using modern hardware given the complexity of the stack, but they do know with as close as is humanly possible to 100% certainty that a correctly configured environment will result in that statement outputting the text "hello world" to a console. They do not need to know the implementation because the contract is deterministic and well defined. Prompts are not deterministic nor well defined, so if you want to verify it's doing what you want it to do, you have to check what it's doing in detail.
Your basic argument here is that you can save a lot of time by trusting the LLM will faithfully wire the code as you want, and that you can write tests to sanity check behavior and verify that. That's a valid argument, if you're ok tolerating a certain level of uncertainty about behavior that you haven't meticulously checked or tested. The more you want to meticulously check behavior, the more effort it takes, and the more it converges to the effort involved in just writing the code normally.
