According to this MSE post the 5 minute grace period has not gone anywhere, but there is more than just the 5 minute timer that determines if an edit is rolled into the previous revision or a new one created.

According to this answer from Shog9:

Edits will be rolled into the previous revision if the previous revision was created by the same author and none of the following conditions are present:

• The previous revision was created 5 minutes or more in the past
• A comment has been added to the post since the previous revision by anyone other than the editor.
• An answer has been added to the post since the previous revision
• The previous revision was a rollback
• The new revision is a rollback

This behavior was implemented in March 2015.

According to this MSE post the 5 minute grace period has not gone anywhere, but there is more than just the 5 minute timer that determines if an edit is rolled into the previous revision or a new one created.

According to this answer from Shog9:

Edits will be rolled into the previous revision if the previous revision was created by the same author and none of the following conditions are present:

• The previous revision was created 5 minutes or more in the past
• A comment has been added to the post since the previous revision by anyone other than the editor.
• An answer has been added to the post since the previous revision
• The previous revision was a rollback
• The new revision is a rollback

This behavior was implemented in March 2015.