can't make gridlines options work with upcoming version 46

[François]

With version 45, the attached json data, and these options for the horizontal axis: {format: 'MMM dd', gridlines: {count: 6}} I get exactly what I want:

I read the release notes here https://developers.google.com/chart/interactive/docs/release_notes but nothing seems to work. I get only 1 tick:

or all of them:

whatever I try