Sorting page and block types not working

Description

It looks like that changing block and page type order is not possible.
Steps to reproduce:
1. Use Alloy template and then add some settings (GroupName and Order) into SiteContentType attribute of TeaserBlock

  [SiteContentType(GUID = "EB67A99A-E239-41B8-9C59-20EAA5936047", GroupName = "AAA", Order = 1)] 

2. Repeat step 1 to Button block (GroupName = "AAA", Order = 2). ContactBlock (GroupName = "AAA", Order = 1)

3. Rebuild the project and go to edit mode, then try to create a new block

Expect: In the AAA group, the order should be: ContactBlock, ButtonBlock and then TeaserBlock

Actual: those blocks above are sorted alphabetically.