When it was initially added to Blogger, the ability to un delete blogs was available only for blogs deleted after March 2009. That's one obvious limitation. Recent discussions make it apparent that there may be at least two other interesting limitations, to the option that provides both a blog that can be undeleted, and a publicly available deleted URL.
- Blogs created before March 2009 may not provide this option.
- Blogs deleted, when the owning Blogger account is deleted, may not offer this option.
When a blog is "deleted" by the owner, its content is taken offline, the URL remains unavailable to the "Create a blog" and "Rename a blog" wizards, and the 90 days countdown starts. Depending upon how the 90 days clock is maintained within Blogger, that's at least one more value that has to be present in the database entry for the blog being deleted. Blogs created before March 2009 may have this value added on the fly - or Blogger may have pushed a database upgrade, in March 2009, for all existing blogs. Either way, that's required code that is not used for blogs created after March 2009 - and possibilities for variations.
Blogs deleted when the owning Blogger account is deleted have always exhibited variations, from blogs individually and intentionally deleted. The 90 day countdown is yet one more feature that may or may not be correctly maintained in this case. Blogger code is designed and written by people, and people make mistakes. It's that simple.