Yes, normally editing the last post in a topic will bump the topic, just the way that adding a new reply to a topic would bump the topic. If there is only one post in the topic, this rule also applies when you edit the topic or category, which are considered elements of the first post. Sometimes this indeed catches people by surprise, but it tends to be specific to the “I have a ton of topics on my forum that are only a single post” scenario.
The editing grace period, which defaults to 5 minutes, has been a built in feature since the very first version of Discourse was released to the world in 2013. For the first 5 minutes after submitting your reply, you can edit that reply as much as you like* and the topic will not be bumped.
I’m curious why this behavior would be such a big problem… can you describe specific scenarios, with examples, where you are constantly “accidentally” bumping topics via editing? 
* However! One tweak we added later – due to spammers – is this: if you change “too much” of a post, we force a revision, even during the editing grace period. There are site settings to control this, and we make a distinction between new users and established users.