It's a followup bug of JDK-8225247.

 java version "13-ea" 2019-09-17
Java(TM) SE Runtime Environment (build 13-ea+21)
Java HotSpot(TM) 64-Bit Server VM (build 13-ea+21, mixed mode, sharing)


Test case:
 import static java.lang.String.format;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.Locale;

public class Java13Regression2
{

public static void main(String[] args)
{
final Locale locale = Locale.FRENCH;
final NumberFormat numberFormat = NumberFormat.getCurrencyInstance(locale);
((DecimalFormat) numberFormat).setParseBigDecimal(true);
final DecimalFormatSymbols decimalFormatSymbols = DecimalFormatSymbols.getInstance(locale);
char groupingSeparator = decimalFormatSymbols.getGroupingSeparator();
String currencySymbol = decimalFormatSymbols.getCurrencySymbol();

String expected = format("1%s234,00%s%s", groupingSeparator, groupingSeparator, currencySymbol); // <<<<< HERE
final String formatted = numberFormat.format(1234f);

formatted.codePoints().forEach(System.err::println);

// prints true for Java 13 build 20 and earlier (Java 12, 11, ...)
// But prints false for Java 13 build 21
System.out.println(expected.equals(formatted));
}
}

Expected/Actual Output:
prints true for Java 13 build 20 and earlier (Java 12, 11, ...)
But prints false for Java 13 build 21