I suspect that the short piles were being used instead of the concrete piles which BW made and used in the 1950s and 1960s. These were principally to protect the bank from erosion caused by wash, and would not have been considered as a major structural feature. Wash was, and is, a major problem as when puddle was originally used to line a canal it was a mixture of loamy soil, sand and small stones, laid in several layers up to 4 feet thick. Clay was only used for very specific problems, such as aqueducts and other major structures. After all, prior to canals being built, there would be no cost-effective method of carrying sufficient quantities of clay to the construction site, whereas loamy soil was often found during excavation of the channel. I have transcribed details re canal puddling from several early 19th century civil engineering books, plus sections from the engineer's reports whilst building the Lancaster Canal, which cover the subject in more detail. These form an Appendix to my recent transcription of 'A Treatise on Inland Navigation', first published in 1817. See: www.canalhistory.co.uk if you would like to buy a copy.
Simplistically, most of the recent structural problems seem to stem from the join between old and new methods of engineering. Both are effective on their own, but can create problems where they connect.