Knot strength estimates are all over the place and hardly ever in agreement. Also, the same knots often go by different namesl.
For instance, on this website Learn Fishing Knots
, the "Water Knot" referred to by Darwin is nothing more than a 4 pass-through overhand knot, whereas a surgeon's knot is a 2 pass-through overhand knot.
In their own write up on that website, they claim near 100% breaking strength on the surgeon's knot but only 60% breaking strength on the "Water Knot". Like most strength claims, they do not cite any testing proceedures, material used, lube used or anything else.
The only things I am strongly convinced of after 59 years of tying fishing knots are:
1) Knots cinched under water are never, ever weaker than those which are cinched after lubing with spit
2) Knots which are cinched with both tag and main line held as close as possible to the knot are never, ever weaker than those which are cinched when held further away.
3) Knots which are cinched fully in one smooth, uninterupted move are never,ever weaker than those which show even a micro second of hesitation while being cinched.
4) Every single spool of leader material should be hand tested till it breaks before it is ever used.
5) A hook ring and pliers are extremely handy when tying heavy bite tippets.
6) It is very helpful to learn to tie the most commonly used knots by feel so that they can be tied at night without light or glasses.
7) added on edit
Leader material is cheap relative to everything else. Don't shortchange the tag.