The early 737's with JT8D series engines initially had a start lever actuation at 15 percent N2 during engine start. Complaints were filed to the engine manufacturer that 15% gave high starting EGT that were worrying people. Following further engine testing, the manufacturer recommended a revised figure of 20 percent N2 before the start lever was raised to idle from cut off. The high EGT problem disappeared and everyone was happy.
Then the inevitable happened and some pilots decided they could drop the EGT even further and let the starter wind up to max motoring before introducing the start lever. Of course they hadn't a clue what other technical factors may be affected by the higher N2 rotation.
In other words they disregarded the manufacturer's recommendations in favour of their more expert (in their mind) knowledge. Of course they had not done measured tests to prove their point nor had they written to the engine manufacturer with their research results (apart from personal opinion) to prove the manufacturer recommendations were wrong.
In every airline there are the smarties that insist their personal opinions should be SOP - certainly while they are in command of the aircraft. As a wise man once said "Without data, you've only got opinion".