I agree with the post above.
Does the installing company have a portfolio of installation pictures? I usually take a few hundred just for personal reference for posterity, so I'd think there's a good chance they have some and those could serve as the inspection.
Once a roof is installed, the details that matter are no longer visible. You can look for gross errors or things like cracked tiles but otherwise, there's not much to see. The key areas for leaks in tile roofing will be valleys, chimneys, and sidewalls and depending on products used, that may or may not be visible on tile edges.
Additionally, I highly discourage having someone not affiliated with the installing company walk all over a new tile roof. The potential for breaking or cracking tiles is not zero and they may not realize it while they walk. It's one thing to walk and risk damage after a massive hailstorm when there is good reason, but here, I don't think it's a good idea. If anything goes wrong and there is evidence someone else was there, the company can use that as warranty denial, and with good reason.
I'd reach out to the installing company for photos or their blessing that it's done properly. If synthetic underlayment products were used, what kind, lead, suitable flashing, bird stop, mortar as applicable, etc was installed, then your inspection will come with the next heavy rain event.
Personally, if the company was reputable and not the cheap option, I'd rest easy, rely on their warranty if an issue pops up, and enjoy the roof.