Thank you for reporting this problem.
This is a limitation of the current spellcheck algorithm that RadSpell uses and unfortunately we cannot provide a workaround for it. I updated your Telerik points for this bug report.
We plan to implement the spellcheck algorithm of Google which should fix this problem. We are not able to provide an estimate date when this feature will be implemented since it will require more time and research, but it will provide better suggestions and limit the incorrect ones.
the Telerik team