I actually agree with you but there are many reasons one could think of why they hypothetically may prefer to observe physically rather than via proxy like ''nano bots''. But to assume that just because they are technologically thousands of years ahead of us means they must understand our technology is a logical fallacy in itself. For example, we are much smarter and more technologically advanced than a 'ant' but we are unable to hack into an ant's antenna systems and communicate to other ants, neither do we fully understand the behaviour of certain animals and how they communicate with each other.
Our idea of aliens ultimately comes down the amazing ability of the human mind to invent what he sees based on the technology and culture of the time period, just like in the medieval times there were sightings of supposed 'dragons' and flying boats/ships in the sky, in the late 1800s there were people that saw flying 'airships'. There are never any sightings of flying saucers pre-1930s.
So why do we assume aliens would observe from low altitude in manned craft? It's because it's what we would do.
Well, no, absolutely wrong. Regarding the ants, yes to almost everything else.
Ants don’t use technology. They evolved. Yes, some biological systems are more complex than anything we can understand. Which is why we can’t make an ant, yes?
But computers are based on universal physics that you have to master to climb the tech tree to the next stage. If you’re at the ftl stage, you understood that physics millennia ago. And you have a vast amount of processing power and instruments that let you look at a chip and trivially reverse engineer it. Physics is physics. After that, decoding the operating instructions is trivial.
tldr: you don’t have to understand ants to build computers. But you do have to understand basic physics to build starships. If you understand physics at fil levels, then silicon based computers are easily understood as a lever is to us. Unless we assume that they are magical starships.
As for those “many reasons”… I can’t think of one that makes sense. Especially if ufos are crashing all over the place. Would you like to say what they are?