We did run the 9.1 installation scripts multiple times in different local machines, never noticed 30 minutes delay to update the Solr Schema. Just check your installation logs if it says "[Success] Completed Request" like the below then no issues with the installation.
It usually takes few minutes to update the solr schema. But it's unusual/rare in your case, may be something else is causing the delay in your machine, Without knowing your local machine configuration and usage, not easy to comment on this issue.
But if required you can verify/replicate this step again from Sitecore Control Panel "Populate Solr Managed Schema" or you can run the URL http://your-domain/sitecore/admin/PopulateManagedSchema.aspx?indexes=all which is in your screen shot to make sure that it was just a temporary glitch when installing the Sitecore and no issues updating the solr schema.
[SitecoreXP0_UpdateSolrSchema]:[Authenticating] http://your-domain/sitecore/admin/PopulateManagedSchema.aspx?indexes=all
[SitecoreXP0_UpdateSolrSchema]:[Requesting] http://your-domain/sitecore/admin/PopulateManagedSchema.aspx?indexes=all
[SitecoreXP0_UpdateSolrSchema]:**[Success] Completed Request**