Let´s think, every  hour would be 1:00, 2:00, 3:00, 4:00, 5:00.

Every other hour skip every second hour, so 1:00, 3:00, 5:00.

Every two hours would be 1:00 plus 2:00 hours so it would be 3:00, next time would be 5:00.

Technically it is the same, but let´s think of every two days.

If we begin at 00:00 [ 12:00 PM ], Feb, on day 8, then every other day doesn´t necessarily has to be On 00:00 of the 10th day. 

We see that in general statements like "I work every other day" or something like that. Meaning "day on, day off". 

With Every two days, it adds a degree of precision, the event would be repeated on

day 10, at the same time (hour) or so.

But it´s me, others may follow a different reasoning. Sometimes both ways can be interchangeable, after all.