Fitting by presets
If you apply the text fitting through the fitting presets, the alignment to the page baseline grid will be kept.
Note: the alignment of text to the page baseline grid will work well only if the Y-position and the height of all the frames in the flow is aligned to the page baseline grid.
Fitting by variable spacing
If you apply the text fitting through the variable spacing, the alignment to the page baseline grid will NOT be kept.
Fitting step-by-step
If you apply the text fitting through the step-by-step, the alignment to the page baseline grid will be kept if you do not change leading, typographical baseline or vertical spacing.