small `Check::instances()` usage cleanup (#8559) #19779

Job	Run time
build_cmake (ubuntu:24.04, true, true)	4m 30s
build_cmake (alpine:3.23, false, false)	3m 38s
build_cmake (ubuntu:25.10, true, true)	4m 46s
build_make (ubuntu:24.04)	3m 34s
build_make (alpine:3.23)	6m 5s
build_make (ubuntu:25.10)	5m 11s
	27m 44s

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