Many years ago I remember being taught about constipation and advice to give patients, one piece of which was to use a lower toilet or use a box to raise the feet to get a similar effect so maybe a lower loo is better for the bowels.
My pet hate is not the height but the width allowed (or not allowed more to the point) for arse expansion when sitting IYSWIM. We stopped at a motorway services yesterday and the combination of a narrow cubicle and a sanitary disposal bin jammed in at the side made sitting very uncomfortable for anybody larger than a racing snake. I don't expect to be comfy enough to sit there for hours but pooing on a slant because I can't get both bum cheeks on there is a bit much
You can toilets for the disabled in builders merchants. They are at least 4 inches higher than normal toilets. We have two in my house as my DH is 6 feet 4 inches tall and has had two knee replacements but still has trouble bending his knees.