I like doing large water changes too - even when there are no fish in the tank
I have tall tanks so even though I drop the water level slightly past the 2/3 mark on the glass height, given that substrate has a major volume contribution in that bottom 1/3 of the tank, it's likely my water change by volume is significantly greater than 70%
So why am I stressing my fish?
Because they respond so positively to the large water changes.
I use a Python system & the time lapse between 50% mark on the glass - then 70% - then return to 50% is NOT long (sorry don't have the actual time but I can complete the water change in under 30 min)
I don't move about in the tank or clean walls etc when the water level is below the 25% mark on the glass (ie only slightly lowered water level from full - less splashing this way)
Perhaps others do their tank maintenance at lowered water levels & that is why they find the water changes to be noticeably stressful to fish.
I also offer a favorite food shortly after water change - the wild caught S vaillanti I have in a too small Q tank (ie they already have cause for stress) constantly request food through the water change process, & immediately gather for their expected food after water change is complete.
I plan a 50% water change in this tank as it's only 30cm high (& I keep low substrate height in this tank as well) - when I accidentally drained more like 80% of the water & fish had disappeared into the back areas, as soon as water level returned to even 50%, fish were back out asking after food, water change complete & they didn't act as if I'd turned their water parameters upsidedown or even sideways
In their natural life, fish experience stress as well, those stress hormones generally "activate", increasing metabolism/catabolites - momentary stress is not the same as continual stress (which strongly suppresses fish immune function among other factors)
I do have some fish that display discomfort with water change, but they are already showing stress colors/behaviour before I've removed even 10% of the water ... and they quickly return to life as normal once the water change is completed.
Most freshwater fish kept in aquaria come from natural waters where there are seasonal changes, even significant temperature & pH swings through the course of 24hours (all this is documented in scientific journal articles), fish from these waters have metabolic mechanisms designed to stabilize their biochemistry against change - I'm much less concerned about matching exact water parameters with these species than those that are endemic to very stable waters.
But anyone that is not comfortable doing more than a 25% water changes, is doing just fine too