I also sent this issue into HTC and the customer service person (John). Response Below:
Hello Jeffrey, I have tried to replicate your issue with the light sensor when on a call with the T-Mobile Touch Pro 2. The T-Mobile Touch Pro 2 functioned properly with the light sensor making the screen go dark when on a call, and remaining on the call screen when light sensor activated the screen. While on a call, I was able to go to the Home Tab of TouchFlo 3D by pressing the Home key on the front of the phone without a password. However, when a password is applied to the phone, the light sensor will cause the phone to revert to the Home tab while on a call the first time the screen is disabled. If you remain on the Home tab and continue with the phone call, every time the screen is activated the Home tab will be displayed. Once on the Home tab and still on the call, I was able to return to the phone screen by pressing the Send Call button once. Once you return to the phone screen and continue the conversation, the phone screen will be displayed. No other number was dialed by pressing the Send Call button while connected to a call. Please feel free to contact us again if you have any further questions. In order to help improve our service I’d like to invite you to take a survey at http://survey.htc.com/worldwide. Thank you for contacting HTC America Technical Support via e-mail. HTC Technical Support www.htc.com/us www.htcwiki.com
I explained to John that my issue was with the Sprint model. Still no change in his response.
I think we need a few more people to write to HTC via their website to make the "problem" more visible. Hitting the send button is an annoying work around to this design flaw.