Monoculture is the attempt to grow one variety of one species and (more or less) exclude the rest of existence in that quest, including but not limited to soil organisms, various insects, some mammals like
mice, rats, and birds, fungi...
Polyculture is the attempt to grow 3 or more species in close proximity. 2 cultures would just be companion planting.
And that's about it. Anything else is pretty much fair game with how one goes about cultivating those species.
The garden you saw probably is in line with synergistic
gardening from Emilia Hazlip. The gardens I've seen using that technique do the things you saw: raised beds, no-till from 2nd year on, no fertilizer that comes from outside the garden, drip irrigation, and spaced planting. There are rules for where you put which plants.
We worked with that model until we realized it was totally unworkable on our site, mainly due to the lack of water and the lack of a balanced mineral base. We now grow much much closer and after working with a polyculture strategy that was very random we are now working to develop better arrangements of plants based on our
experience of how plants grow.
Hope this helps,
William