Well, Rhizo means a serious issue and it's been induced in control tanks several times using nothing more than CO2.
I had my first dealing with it in 1994 with DIY and adding 160W over a 55 gal tank. I can induce it pretty well if I reduce the CO2, other species also appear.
High light is a great way to make the rounds with algae.
High light + DIY is even better.
You can claim you did everything perfect, but no one does.
You have to make double sure.
Everytime I said that, I found something I over looked.
Algae just does not appear when you take good care of the tank and stay on top of things, many like to believe so but that is not the case.
Algae are induced for defined reasons, they can be tested and shown to be inducible as well, that shows at least one cause(there may be more).
When those caused are not present, you cannot induce the algae.
But you have to be able to produce a control tank and be willing to manipulate the CO2, light, nutrients etc to see if there is an effect from the treatment.
Then you need to get rid of the issue, then clean things up, then try it again.
Do this 4-6 times or so, then you have a good idea.
But you have that much control, you likely do not have algae issues to begin with.
I use to think the same things I read from folks also.
But I learned, as many do as they become wiser and more experienced in the hobby and with algae.
There's no secret about it really, you just take good care of things, do water changes, prune and keep it well stocked and clean, focus heavily on good CO2/cleaning the filters etc.
Mostly basic stuff.
I over look cleaning my filter every so often, but I I know my self enough to check there before blaming everything else.
While CO2 might be one cause, I'd say it's the lion share and drives most changes if used, and if you also have a lot of light, then you are prime for this, there are other causes.
Cleaning filters, reduced flows, lack of water changes, changes in the tap water KH season to season(It was always 5, till one day it went to 1!). Poor test kit methods, always something it seems.
You can also use the plants to check, good Riccia bubble production was one way I used to make sure I had enough CO2 when I first got MH's in the late 1980's. Worked quite well. That's when I started adding 30ppm of CO2.
15 ppm was fine if you used a shop light etc or low light as most everyone did at the time.
Just keep after the tank, focus a lot of CO2, making sure you have more than enough during the light peroid, clean the filter, add zeolite etc, do water changes, add Excel and then add then ferts and do water changes there after.
Rhizo does go away pretty easily with Excel and Blackouts. Water changes etc ought to clear things up well after 2-3 weeks time.
I do not think you will have trouble much with it hereafter.