This may be, but many of us associate "Make an offer" with a higher "Buy it now" price where offers below the current visible price are expected. "Make an offer" makes it look like it is NOT an auction with prices going up, rather a offering with the price expected to go down. If some seller wants to use that feature, that's fine. What is not fine is when eBay inserts it without my wanting it and without my agreeing to it.
Exactly. There can be confusion when the potential buyer knows little about what they are looking at. Some time back I listed an item on Ebay for $60, which was about a third of what it was worth but I wanted to get rid of it since I had it too long. I got several offers from the same person and I declined them all (and I had not listed it with that option). He finally bought it at the list price but left me a neutral feedback since he was unhappy I would not accept the lower offers. Just one of the many reasons I dont sell on Ebay (though I do try every few years).
You are agreeing to it when you use their new quick selling tool, according to their terms. If you don't like this feature you can use the advanced selling tool and you can set your own Make an Offer setting for your auctions. You can also remove it from all your current listings by selecting all active selling items then clicking edit, select all, edit fields, best offer -> remove from all, and save.