a computer is something which computes. This device, in a very analogue fashion computes the position of the planets at a specific time. So what if you have to manually power it? That just means it still works when the power's off. It certainly is a computer, just as your pocket watch is.
But the information is static in both a pocket watch and this device they created. To me, besides the mechanical gears that make it move, it's still no more different then a sun dial based on the information it provides, yet would you consider a sun dial as a computer? Yes, the first technical computer I believe just coded in zeros and ones and could only do basic calculations and the sort. Now it too had to have its information preprogrammed and determined for it to work, much like this device, but why did the term Computer start to take form with the first computer and everything else before that was basically called a machine?
With an old clock, a sun dial, or even this greek device, the information is static and set based on it's design.... there is no computing required and certainly no more then a paper calender hanging on your wall..... the only difference is that it is mechanical..... but it's not doing any calculations. The gears move to reposition the pointers to where they were already predetermined by a human when designing it.... there is no central processing unit, there is no calculations, anymore then an old wooden abacus counter.
The word robot comes from the czech word for forced labour, or slavery. So basically anything which does a job for you in an independant fashion is a robot. Now admittedly these things only ran for a few minutes on their own but that's still robotic in my opinion. They were also programmable in that the same robot could be made to do different things each time it was set up. To some extent that's what sets these devices aside from the ones you showed in your picture, but there is a case to be made for calling those robots too, since you could program them to go backwards.
those rubber band boats could also be programmed to go backwards by just simply spinning the propeller in the opposite direction then normal.... it might not work as effectively as it would going forwards, but it's the exact same principle in design.
and you mentioned
"basically anything which does a job for you in an independant fashion is a robot."
What Job does this stick on a couple of wheels and a string do to classify it as a robot? It doesn't seem all that sturdy to drag around anything heavy or useful, and back then, I imagine dirt roads would have done a number on this device.
Quite honestly, it'd probably be more practical and take less energy to do the job yourself then it would be to string this thing up, revolve the string to make it move, set the weight/direction, etc..... only for it to move a few feet away and then end up having to do it all over again for another few feet.
They're interesting devices, but I feel using the term Robot and Computer is a bit exaggerated based on what they are.