Template string downlevel to ES5 escapes more Unicode characters than necessary

TypeScript Version: 1.8.10

Typescript compiles template strings with Unicode characters incorrectly.

Code

var test1: string = 'test'; // Normal string (only English)
var test2: string = `test`; // Template string (only English)
var test3: string = 'тест'; // Normal string (Cyrillic)
var test4: string = `тест`; // Template string (Cyrillic)

Expected behavior:

There should be no significant difference in string representation, no matter language they are using. Since this is Unicode anyway. You can see expected behavior on standard, singleline strings. This behavior I would consider normal, expected.

var test1 = 'test'; // Normal string (only English)
var test2 = "test"; // Template string (only English)
var test3 = 'тест'; // Normal string (Cyrillic)
var test4 = "тест"; // Template string (Cyrillic)

Actual behavior:

Multiline (template) strings with none-English characters becomes encoded.

var test1 = 'test'; // Normal string (only English)
var test2 = "test"; // Template string (only English)
var test3 = 'тест'; // Normal string (Cyrillic)
var test4 = "\u0442\u0435\u0441\u0442"; // Template string (Cyrillic)

Link to official playground

Reproduce the Unicode template-string case in the linked official TypeScript playground, comparing the normal string and the ES5-downleveled template string. Trace the compiler behavior responsible for the differing output and verify that Cyrillic text is emitted consistently without changing the expected runtime value.