Is it safe for dryer vent ducts to overlap in different directions?
You basically answered your own question.

No one here should answer you and say "it's safe" and even if they did, would you blindly trust that as the final answer?

Is it safe to walk over Niagara Falls on a tight rope? If you are Nik Wallenda, yes. Should he do it? That's debatable, but he did - and indeed, many safety precautions were taken.

Dryer vents are NEVER EVER EVER "Install and forget." All families drying clothes are different sizes, and the clothing they own are different materials, and qualities. Even the dryer itself has a YMMV (Your Mileage May Vary) effect on the amount of lint passing into the tube. Eventually, the tube will have to be cleaned.

Technically speaking, at any given point in time a dryer tube with lint in it could catch fire (think cause and effect/affect; intentional pun). So anything you do that negatively impacts the desired laws of physics (as you have correctly described their relevance in your pictures above) increases the mathematical likelihood of an eventual fire by some factor.

The real point is that you should install it the right way. Regardless of if you follow through with installing it the right way, you should develop a schedule of checking it and cleaning it at regular intervals.

I do not sell nor necessarily advocate this product, but products like this are made that are supposed to give you feedback on when it might be time to clean your duct work. I bought this device and in about 6 months will be checking my recent duct work install to see how clean it is and probably clean it for good measure.

Whatever you choose to do, I recommend you go with what gives you peace of mind and just be sure to check it at a regular interval regardless.