If you are looking for a definitive answer here you wont get it.
I have one for you. There is no scientific basis that deer sense electromagnetic fields in the manner that the HECS suit is supposed to protect against. They claim the suit is based on science because some birds NAVIGATE by electromagnetic fields (but no science saying birds detect predators via electromagnetic fields), that field sense the electromagnetic fields of other creatures in the water (which is very true and fish have a highly develop lateral line system and other sensors to do this, but deer and such aren't what we are talking about), etc. Now they note in their promo video that the electromagnetic field given off by animals is very similar to the field given off by the earth by which they navigate and therefore they THEORIZED that maybe animals with their "uncanny" ability to detect us when no other stimuli were present might be due to them detecting our electromagnetic fields. WOW! REALLY? Never mind all the other senses used by animals to detect predators.
What is really striking is that the same exact sorts of success claims made by the HECS suit are made by folks using various patterns of camo, using ozone generators, and using scent control clothing. They ALL claim the same miracle results. They all show videos of people in proximity to animals.
There are lots of stories where people were close to deer that they attribute to the HECS suit, but it really isn't that hard to be close to deer or many other animals.
Here is a guy, NOT in a HECS suit, hunting and has the deer walk right up to him. He must not have an electromagnetic field...
https://www.youtube.com/watch?v=3Jy4rKb4vGoThis guy touches a buck with his arrow during archery season...
https://www.youtube.com/watch?v=7p7c3FokGgQThis guy stalks and touches a deer without a HECS suit...
https://www.youtube.com/watch?v=0A4eX1YYg0YThis lady is within 4 yards of a bull elk, no HECS suit...
https://www.youtube.com/watch?v=bP38tYhyhW0This guy sneaks up on a lounging deer. Apparently, he has no electromagnetic field...
https://www.youtube.com/watch?v=7Y50PY4v6ScGroup of hunters meet a buck...
https://www.youtube.com/watch?v=SlSC6fWrfNcSo how are all these hunters with their electromagnetic fields running electronic recording equipment with electromagnetic fields managing to do this without HECS suits? Miracles, right?
I put it in the category of products like the miracle fuel savers such as vortex systems, magnets, etc. People swore up and down, backwards and forwards that the systems work and they did, but they did not because the systems did what was claimed, but because people changed their behaviors. That would only last for a while however, and then people would return to their normal driving habits.
https://www.tornadoair.com/https://www.popularmechanics.com/cars/a310/1802932/