It is astounding how many passport control staff don't understand the visa system. With the new online visa you could go for the last 90 days of the 180 , go to Rhodes for the day and return and use up the first 90 days of the second visa - meaning you can be in Turkey for 180 days in a row with a quick hop over to Rhodes or Meis in the middle.
What they'd make of that is not worth wondering.
There is simply no situation, however you take the 90 days within the 180 on the visa, where upon expiry you cannot return for 180 days. The maximum would be if you used the first 90 days of the 180, then left - and then you couldn't return to Turkey for the next 90 days.
But even then I reckon you could