Why doesn't TurboTax follow the instructions of IRS. Please let me know how can I submit the extension request?
There is no need to include the non-resident spouse on a resident alien taxpayer's application for automatic extension of time to file a federal tax return.
The non-resident spouse is not yet required to file a tax return, and the resident alien taxpayer does not have to declare a filing status (MFS, MFJ) with the request for extension. Since it will ultimately be a joint return, you can request the extension yourself.
If you don't feel comfortable with this approach, you can print out Form 4868 from the IRS, fill it out, and mail it on or before April 18. Complete mailing instructions are on the printout.