Here is my response when I emailed Chevy about this:
Thank you for contacting the Chevrolet Volt and Spark Advisor Team. We always love to hear from owners and appreciate the opportunity to assist you.
As stated in your email, the my.chevrolet.com website is not set up like the myvolt.com website. The my.chevrolet.com website is offered through General Motors for all Chevrolet vehicles and therefore, it provides general ownership information. At this time, there are no plans to change anything on that website. One day Spark may have its own website like the myvolt.com, but unfortunately nothing is available yet.
For your information, myvolt.com and the remote link app are both operated by Onstar. You can contact them by pressing the blue button in your Volt or 1-888-667-8279.
Please feel free to email us anytime with more questions or contact the Volt Advisor Team at 1-877-486-5846. Our hours of operation are Monday–Friday 8am to 11pm (EST) and Saturday from 11am to 8pm (EST).
We are happy to have you in our Volt and Spark families and look forward to serving you in the years ahead! Safe driving!
The Chevrolet Volt and Spark Advisor Team