Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 23.39%. Comparing base (b46b6fb) to head (e0c518b).
Report is 2 commits behind head on master.

@@            Coverage Diff             @@
##           master    #1393      +/-   ##
==========================================
- Coverage   23.40%   23.39%   -0.01%     
==========================================
  Files          25       25              
  Lines        4230     4244      +14     
==========================================
+ Hits          990      993       +3     
- Misses       3077     3088      +11     
  Partials      163      163              

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So this looks good provided you do want to take a breaking change here. One reason to think twice, I checked with TF they also have this structure:

			"default_tags": {
				Type:        schema.TypeList,
				Optional:    true,
				MaxItems:    1,
				Description: "Configuration block with settings to default resource tags across all resources.",
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"tags": {
							Type:        schema.TypeMap,
							Optional:    true,
							Elem:        &schema.Schema{Type: schema.TypeString},
							Description: "Resource tags to default across all resources",
						},
					},
				},
			},

I'm not sure but I think it's because there is some code around called TagIgnoreConfig and so forth, and possibly there were some plans to make the defaultTags do more than just add tags in the TF Provider but also have some sort of "policy" impact on transforming existing tags. Perhaps that's why this was modeled as a struct so new fields could have been added later. But they never were.

Perhaps in Pulumi the answer to this sort of thing is using transformations and it's never going to be needed anyway.