There isn't a triathlete racing (pro or otherwise) who should be worried about lactate testing in swimming.
a bit of background, I am MD in anesthesiology/critical care, so it's a bit of second nature for me to poke with needles and analyse physiology.
I have started triathlon around 2015, learnt basic freestyle to survive triathlons. I can enjoy swimming but I will never be a swimmer, I cannot go 4-5 times a week to the pool, that's just not doable. I have to deal with the few hours I have to enjoy my sport the way I like it :)
Since I have interest in human physiology, I have not waited for You Tube videos to think about metabolism in sports. Lactate measurement is one tool to question my practice and learn. I get the fact that the big picture is more important than a tiny detail,. You might think that I am lost in a fad with lactate testing, but I think that I am not in this position. I find that lactate testing can be interesting even for the mere amateur. Lactate testing has taught me that I have a bigger space than I thought to work endurance on the run and on the bike. I had the tendency to do some easy work too easy. It might not be the most usual mistake, but I can tell you than doing lactate testing, I have discovered that I could sustain higher wattage during endurance rides.
For the swim, it might be the other way around. Because of my lack of "arm & back" muscular endurance, I might overflow the system with lactate which shuts off lipolysis and builds fatigue quicker. My RPE might be a little bit skewed while swimming. Even if I feel easy (and remember my HR was 60% HRmax), I maybe should go slower, thats why I find lactate testing interesting.
Then we can go on the "learn swim technique" debate. I have no triathlon coach who can teach me from the deck. I have to deal with my environment. Masters swimming is not triathlon swimming and I just cannot go with this kind of people since it's highly competitive and I have not enough time to allocate. I could also watch hundred of swimming videos, but again I find that it's super hard to progress when you learn to swim around 40 yo. At some point I can train to have enough endurance to deal with IM distance (done it in 1h05) but I think I do not have a lot of room to get better at swimming with my actual life. And I'm ok with that. On another side, I see people lost with technique, doing a new drill every 50 meter and I am not sure that's effective.
Is there people who have followed Lionel Sanders Discords on this ? (I didn't)