It sounds like the OP is asking if the council isn’t liable for not advising the developer correctly. My view, it’s up to the developer to check and if they planted the wrong plants, then it’s a defect. If they did so because the council told them to, it’s up to them to take it up with the council.
Either way, the owners should not be paying a cent towards this.
And if plants were planted that the owners wanted, who is responsible?
The developer could have got the list of plants they wanted, but planted the wrong amount. For example, the owners wrote bushes, trees and flowers, but the developer planted 2 trees, 10 bushes and 3 flowers. I.e. technically the developer has planted everything that is needed, but the owners do not like the proportion of these plants, they want 10 flowers, 5 bushes and 3 trees, but they did not tell about it at once.