New Greek Design metrics query?

In preparation to add Hinting to the new Greek designs, I noted that as well as the shape updates, there are some metrics/advance width changes in the new Greek designs?

I wanted to check before we go further with the hinting, that advance width changes are expected? I seem to recall that the idea was to match the metrics of Roboto static 100%?

Example:

Shipping Roboto static
Lowercase ‘lambda’ uni 0x3bb Advance width = 1134

Classic Roboto VF
Lowercase ‘lambda’ uni 0x3bb Advance width = 1134

New Roboto Greek Design
Lowercase ‘lambda’ uni 0x3bb Advance width = 961

https://github.com/TypeNetwork/Roboto-Flex/tree/master/fonts/