Problem with not unique web ids for Sharepoint Online web sites created with Fast Site Collection creation

When you create modern Team or Communication sites which use Fast Site Collection creation (not only from UI but also e.g. using New-PnPUnifiedGroup cmdlet) you may face with unexpected surprise: web id of the root sites (SPWeb.ID) of different site collections created this way may be equal!

Connect-PnPOnline https://{mytenant}.sharepoint.com/sites/site1
Get-PnPWeb
Title             ServerRelativeUrl        Id

-----             -----------------        --

site1             /sites/site1             {guid1}


Connect-PnPOnline https://{mytenant}.sharepoint.com/sites/site2
Get-PnPWeb
Title             ServerRelativeUrl        Id

-----             -----------------        --

site2             /sites/site2             {guid1}

This may be crucial if you have custom features which depend on web id. At the same time site collection ids appears to be different (SPSite.ID). Which means that if you have custom feature which identifies sites by SPWeb.ID only it will be safer to modify it so it will use pair (SPSite.ID, SPWeb.ID) to identify sites.