docs(syntax): more comments for `ReferenceFlags` #22626

Job	Run time
Benchmark (lexer)	1m 37s
Benchmark (parser)	2m 13s
Benchmark (transformer)	3m 23s
Benchmark (isolated_declarations)	1m 52s
Build Linter Benchmark	3m 0s
Benchmark (semantic)	2m 9s
Benchmark (minifier)	3m 17s
Benchmark (codegen)	1m 51s
Benchmark (sourcemap)	1m 49s
Benchmark linter (0)	3m 32s
Benchmark linter (1)	1m 34s
Upload benchmarks	33s
	26m 50s

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