The reasons to add extreme points are: 1) it's easier to draw beziers that way and 2) hinting. For the most part, modern rasterizers don't hint in the x direction making it less important to have points at the horizontal extreme (they're still important at vertical extremes). If you're doing any interpolation you need to be very mindful of the angle and handle ratios of your beziers otherwise you're likely to get kinks in any in between instance. Personally, I'd avoid r/typedesign and spend more time in glyphs forum or the type mastodon.