Old drives allow ×4 on a CD-RW-HS(×10)?

The CD-RW high speed is rated for ×8-×12, so drives mostly only offer ×10.

But several old drives such as the SH-S182 offer to write at ×10 or ×4. This can be very interesting.

I can not test, whether ×4 works, because that S182 was from a dumped school computer, and does only write CD-R. Even if I write CD-RW×10 at ×10, it does just effectively blank the disc.

What purpose did writing a CD-RW×10 at ×4 speed preserve?

The S182 surprisingly ONLY fails burning CD-RW, not even DVD-RW×6.

DVD-R is detected as blank nearly always, DVD+R sometimes. Dual layer: same effect. RW is never detected as blank.

Manual mentions “DVD+RAM”,