The Hammers face Chelsea tomorrow and Curbs said: "I don't think the style has changed.
"They play a certain way. It suits them. They are talking about it as if it's a different game. The side was established before and there has been no change to personnel. All that has happened over the past couple of months is that they have got their players back."
"When Grant took the job on, he must have thought: 'I would win more than I will lose with this squad,' " Curbishley said. "He has gone about his job quietly and let the team flourish.
"But the foundations and squad are what Mourinho left. Grant has picked up the results, which helps. They are looking confident. If you wanted to have a change [from Mourinho], he was the perfect solution. He is reserved, someone a little bit different to what they had."
Curbishley said that he did not have a problem with Grant not having the required coaching qualifications at present. Grant has an A-licence but must attain his Uefa Pro Licence to remain as first-team coach in the long term. Curbishley sits on the League Managers Association executive committee, the organisation that has maintained that managers must have the necessary badges to work at the highest level.
"He is vastly experienced," Curbishley said.