Hi op - I am that poster I think

Like others said, different pools handle this differently. As you heard, some pools you have to already be swimming some normal strokes. Dominion Hills is like this. Our pool, Forest Hollow (we are Arlington residents but haven't gotten off the list at Arlington pools yet, probably calling myself out to anyone that knows me) which is doable from Falls church takes a different approach - if you are 4 and comfortable in the water they take them and work with them. It is fantastic.
Until recently Forest hollow has not had a waitlist, I think they JUST filled up for this summer. But that means there will definitely be some spots when things open up in the spring as there is always turnover in pools. So if it works for you, email forest hollow and ask them to let you know when membership opens up next year.
https://www.foresthollow.com/
Otherwise, what I did was basically look at the pools in the area and on the website you can usually find details of their swim team and "mini" teams. I don't know how many operate like forest hollow where it is more open, but most pools have a mini team where you don't have to be able to swim a 25, that is the job of the mini team to teach you. That is kind of the whole point, to help kids get to a point they could do a more typical practice. Sounds like some are more intense but there are definitely other pools that do this more developmental approach.