Possibly. They let you pick your nearest server, and HE is a tier-1 ISP which a lot of your packets may traverse already.

It won't add much if you pick an appropriate tunnel server.

All my packets go through Seattle, using a Seattle tunnel server adds negligble latency.

But as someone else said, being connected with an he.net tunnel gets you marked as undesirable traffic these days, so that's annoying.

Yeah ok if you already live near one of their locations, then it makes sense. But in my case it would have to go through an entirely different country, which would be fairly inconvenient.

HE has a lot of points of presence in North America and Europe: https://pop.he.net/ , so latency should be negligible there. Elsewhere, yes you might see higher latency.