I know what you mean. My first custodial employment was with a professional cleaning contractor as a supervisor of a traveling project crew. We extracted/cleaned carpet and restroom tile among other things.
My school restrooms right now really need the grout cleaned as they have build-up & many years ago someone had the

idea of applying floor finish/wax to ceramic tile floors. The wax has been removed for the most part on the surface of the tile, but not ias much in the grout lines. We haven't been able to get stripper for this purpose as yet.
Unfortunately, the district custodial supervisor isn't supportive of allowing me to use an acid restorer and the district doesn't have a 'Spinner wand' used to powerwash/vacuum the soils at the same time. It's all part of being 'Green' and not wanting to use acids or harsh chemicals. We do use a 'Compass' machine by Windsor, but it doesn't have the PSI needed to remove the heavy build-up....so I just make due the best I can.
Yes....unsealed grout lines can also be a source of odors.
Regards,
Bradley.