No dosing is just lazy in my opinion. Anyone who is not willing to perform a simple tritiation to ensure stability of their eco-system should be asking themselves why they are not. I assume the reason behind your no dose stance would be no testing before hand.
It's also pretty dang hard to over-dose a 2-part system. Even if you dosed it every day your tank would eventually adapt and begin to utilize all of it. Obviously if you have 1 coral you shouldn't dose yet... What's going to get out of whack with a 2-part dosing option though? Everything is supplied in a balanced ratio. And I mean unless you start to get around 8 Meq/L KH
, 550ppm calcium, and 1900ppm mg
you're not really over-dosing.... So it's really hard to get things out of whack with a 2-part. You really don't even need to test if you have enough corals.
You should be able to just tell by coral growth how much they're using. I think most hobbyist are scared to dose 5 liquids a day because they just don't know what those chemicals are responsible for and how to just look at the tank and see their effectiveness.
EDIT: I also mentioned in the original post how relying on water changes for your hard corals will likely be negative for your live animals as it is very easy to get too busy or forget to do the required water change. And to the same line of thinking you had around water changes slowly picking at nutrients, at this point water changes only slowly re-supply the tank with needed elements. It's more often a tank relying on water changes with hard corals for elements will eventually suffer from low magnesium or low calcium... Very typical for them to also run out of trace elements. Most aquarist do not know you should dose trace elements in combination with calcium..
Sometimes it's just easier to dose a balanced equal portions 2-part system like Seachem Fusion or B-Ionic.
Most of the time aquarist are just too scared too dose. After it becomes a simple method it'd hard to believe it was never done. Especially once the benefits are clearly seen.
You'd be amazed at the growth results you'd get from a calcium reactor or a multi-day dosing auto-dosed
Do you use kawlk for top-off or do you really expect water changes to always be enough?