Please add "Match the document units" as an option within SVG Options. If this is left unchecked the SVG will use the default SVG unit of pixels, if checked the SVG will adopt the units used in the working document.
Why?
Historically when saving an AI file as an SVG the width and height of that SVG would be set in pixels regardess of the units of measurement used in the document, at some point in the last couple of years that changed, the units used in the document were matched in the SVG.
This is troublesome as a lot of third-party apps only recognise pixels. For example I use SVG files for a CNC router and the firmware crashes if you use anything but pixels.
Current hacks
Save the SVG, open it in TextEdit and then manually chang the width and height of the SVG to match the pixel values used in viewBox.
Right-click on the document rulers change the units to pixels and then export the SVG. Once saved, revert the rulers back to the working units.