No offense intended.
Not offended at all! I believe that's exactly what you heard and here's why - pond clean outs are the bread and butter of ANY - not just Aquascape - pond builder's business. You build one (or if you're lucky - two or three) ponds for a customer and that's the last you hear from them. If you get them on a regular clean out schedule, you have an income stream. I don't fault them for it as it's a business model that works. And honestly, many people WANT the "new pond" look of sparkling clean rocks and fresh clean gravel or they don't want to mess with their pond at all. Some contractor's have customers on weekly or monthly schedules - they show up and groom plants, add products, check water levels, etc - all well and good for those who wish to have that kind of service. Most of us here are hand's on pond people who love the messing around that goes with the pond. Also great.
But breaking a pond down for cleaning is not necessary and causes way more problems than it solves. (New pond syndrome, anyone?) They will also sell you algaecides and bacteria in a bottle and all kinds of other products designed to keep your pond healthy - again, I get it. It's just not necessary. And unfortunately it's knowing that these ponds are "supposed to" be power washed every spring that leads to the belief that they cannot sustain healthy fish because of the way they are constructed. Like you, I have visited ponds that have not been broken down in 10, 15, 25 years. My own pond is in it's 7th season - never cleaned, never changed the water, gravel bog is my only filtration, a handful of big koi, all healthy, happy fish.
I have loads of respect for what Aquascape has done and is still doing to promote the garden pond hobby. As you said - it's a particular kind of pond with a specific purpose. When people start trying to use it for high density fish loads they will run into trouble unless they make modifications.
Exactly this - build the pond for the purpose you intend to use it, and you'll be a happy pond owner!but they also decided to add very large schools of koi and operated at the 20 to 40 gallon per pound levels that this type of pond was never designed for.