Transmission designed for 10-15 min cold start delay

[Ironwill5]

Brand new to forum and Toyota. I have an '08 Yaris, 4 dr. automatic. At least 2 months ago I started noticing a delay in shifting. It has slowly become more noticeable, especially 3rd to 4th. My b/f was riding/driving with me one day and he said "what's the noise?" "oh, you notice it too? sounds like the engine is whining, an audible high pitched hum. Been happening 'recently' " says I.

Took it to the dealership where it was orginally purchased (not by me) here in Texas just down the road. Took a service manager for a drive. I asked him to listen for the lack of 'proper' timing in the shift between 3rd and 4th. He agreed it was delayed. I unfortunately offered "I seem to notice it happening more when the car is cold." He jumped on that comment and said 'the ambient temperature outside can make a diffference.'

This is Texas. Not Minnesota, not Alaska. Told him I bought the car in January and it was fine. This is a 'new thing.' Car has 31,000 miles on it. (I have a long commute, mostly highway miles on a car that is still newish). Under warranty.

Left it at the dealer last night so they could check it first thing this morning. Presumable that means diagnostics and a test run to see if they can immitate what I'm hearing.

Service manager said "the car is designed for a cold start shift delay of between 10 and 15 minutes." That doesn't sound right to me. This is a NEW problem, started happening in 80 plus degree weather and is growing more noticeable. Again, this is Texas. I am waiting to hear back on what they find. Which, could be nothing, but there is a problem. I know my car.

Sorry to say I think there is a little, "you're a woman, what could you possibly know about a vehicle besides how to start the engine and drive it." Pretty old-school, male dominated hierarchy here.

Crazy maybe, but not stupid. Anyone know about this "design" in the car. I say it is BS. Maybe a solenoid issue or a chip isn't communicating properly, but something somewhere is not happening. This is a newer/recent problem.

What do I say to the guy if he comes back and says,... 'yeah, it's the cold start delay in shift designed into the car.' Also, he told me when he called me this morning, "you know, I've had 2 other cars last week that came in for this same problem." I am tempted to say, "ok, great call them and let me talk to one of them."

Thoughts anybody?