Alleochemicals produced by plants, their concentrations and ability to inhibit algae(and same species growth) is not a well understood, nor is it readily applied to aquariums because we do not study our tanks at the bacterial and microscopic level. The mechanism by which healthy plant mass inhibits algae, the causation is not known but the correlation clearly is well known.
Concentration of Alleochemicals and BB being reduced by water changes either too large or too frequent is not something that has been proven or studied much in a robust way. Stressing plants by changing nutrient concentrations too abruptly (like 50% water changes) is also something not studied or well proven but in general this notion is supported by many aquarists.
is not alone, there are many experienced Aquarists who don't advise changing more than WC more than 25-30% at a time due to potential loss of Bacteria or for reasons they can't explain except it is preferable for their plants and equilibrium to keep to a smaller water change schedule and dose more lean. My tank has found a nice equilibrium where I don't want to dose too much (I am significantly leaner than PPS-PRO) nor let things bottom out with large water changes.
The correlation between TOCs and lowering them by water changes, and that cleaning up dirty tanks and removing organics does aid in reducing algae is more readily adopted.
The two ideas are independant of each other(and somewhat contradictory), so that vague general advice falls apart and leads to debates, that is why I prefer to look at specific cases.
When someone has BBA more often than not it is due to poor maintenance practices, too much light and/or organics, the common and most effective way to get rid of it involves manual removal, water changes, and then reduction in light as prevention. Once unhealthy plant matter is present, there will be an increase in organics the only prudent way forward is removal by mechanical means, primarily pruning, dipping, and frequent water changes.
However if you are setting up a hardscape focussed tank, low tech, or many other types with lean fertilizer regimes and less frequent water changes it is often not beneficial to change too much water.
There is merit in both positions but not if taken out of context.