What does the light hinting option actually do?

[Tatsuyuki Ishi]

Hi folks,
I have a question regarding light/slight hinting today.

The light hinting mode is generally described as a mode which results in
vertical-only hinting [1]. However, in a later article [2], it's described
that the v40 TrueType interpreter will also do its best to ignore
horizontal hinting instructions.

So is there any difference between light and full hinting modes now, apart
from the fact that the former uses autohinter while the latter runs
TrueType bytecode?

Tatsuyuki

[1]
https://www.freetype.org/freetype2/docs/hinting/text-rendering-general.html
[2] https://www.freetype.org/freetype2/docs/hinting/subpixel-hinting.html