Google Search Console is now attributing the performance figures of each URL to its canonical address, even if the user clicked on the original, non-canonical search result.
The purpose of the change is making data clearer. If two users reach very similar "men's trousers" pages (which the only difference between them is the order of the products) performance data will be united and shown together.
As a result, there will also be a change in alternative assets. For example, a separate mobile version (m.website.com) in oppose to the desktop version. Most of the data on these secondary assets will be merged with the data of the canonical address, so reviewing data of the Alternative assets will no longer be relevant on sites that do not have unique pages on each version.
However, it will still be possible to filter the page's performance on mobile / not mobile within the performance report, while examining the canonical property.
Google gave the following example for a hypothetical website which all of its mobile have a canonical (primary) desktop versions.
Before the change:
• 1,000 clicks and 5,000 impressions appeared on the main (canonical) asset.
• 700 clicks and 3,000 impressions appeared on the asset's mobile version.
After the change:
• The primary asset will have 1,700 clicks and 8,000 impressions.
• On the asset's mobile version, 0 clicks and 0 impressions will appear.
Specific Page - Before Change:
• 200 clicks and 1,000 views in the canonical version.
• 150 clicks and 800 views on the mobile version.
Specific page after the change:
• 350 clicks and 1,800 views on the canonical site.
• 0 clicks and 0 views on the mobile site.
As you can see, in this case it would be pointless to examine the data in the alternative asset.
What to do if you did not prepare in real-time?
Google stopped providing the old data as of April 2019 and in fact recalculated all the data retrospectively since January 2018. If you still see large numbers in the alternative property or duplicate pages in the performance reports, you should make sure the canonical tags are properly set. This could be done using the URL checker tool.
In addition, it is recommend to verify the ownership of your domain using DNS records, in all forms - with and without www, with and without SSL (http and https). See guidelines here (under "DNS record")