It is also very hard to have a realistic estimation of how much work your partner is actually doing, because obviously they are doing it and not you. So it is somewhat obscure to you and their share appears smaller to you. If you want to share work equally you should be prepared to do what you perceive as ~70% of the work load.

On another note: I feel like yard work is a strange example because in most cases work in the garden is a rather voluntary thing. Nothing bad usually happens if a garden is neglected a bit, unless you are relying on it for produce. Granted, things can overgrow, maybe a bush is removed rather sooner than later, but the household is just a huge never ending chain of responsibilities and important garden work is rather sporadic. Household work just needs to be done to ensure there is food on the table and clean clothes in the wardrobe.