For the Monastic Tradition "Way of the Four Elements" in the D&D 5e Player's Handbook (p. 80-81), some Elemental Disciplines allow the monk to spend ki points to cast a spell. For these spell disciplines, additional ki points can be spent to cast the spell at a higher level than its minimum, but there are specified limits to "the maximum number of ki points you can spend to cast a spell in this way".
But other Elemental Disciplines are not called spells and not implied in any way to be spells. Three of these Disciplines do provide a similar way of increasing the effects by spending more ki points. Fangs of the Fire Snake allows spending just 1 additional ki point for a total of 2 points.
However, both the Fist of Unbroken Air and the Water Whip disciplines say you can spend 2 ki points to cause the initial effect, "plus an extra 1d10 bludgeoning damage for each additional ki point you spend".
Is there a limit to how many ki points a Monk can spend on either Fist of Unbroken Air or Water Whip, or how much extra damage they can do, other than the Monk's total supply of ki points?
Just from reading my Player's Handbook (First Printing August 2014 "includes corrections"), it looks like the answer is no, a Monk can always spend any amount of ki points they have available for these disciplines, since the only limits mentioned are for spell casting, and these disciplines are not spells. But this seems surprisingly inconsistent, and a rare potential for doing a huge amount of damage with one action. Has anything changed or clarified this otherwise, in later revisions, errata, or comments from the designers?