I think actually they illustrate that sometimes it is worth pushing the boundaries. One of them is the sole shrub on a small island in the pond (not waterlogged as the pond is concrete lined), and has a rather lovely bonsai-ish form, even if its flowers are disappointing. It is a rather lovely feature. No doubt an even more spectacular effect could have been created with a suitable maple (though they don't like chalk either), but by chance that one works. The other one is just part of shrubbery, and just occasionally gives a good show in spring. It's a big enough garden he can afford to have a few occasional performers, especially since these survive with no attention whatsoever. Some of the in-their-element trees, on the other hand, are costly to maintain requiring attention from professional tree surgeons from time to time.