Yes. For most people it's more like a "schema" or a lossy compression. It can be placed in space, left or right or above or below other image-fragments, there can be colouring, shading, motion, sound. But it's not a faithful bike-image, although it's hard to notice that unless you try to draw it.

There are also other reasons why mental visualization doesn't necessarily mean one can draw it faithfully. For me, mental imagery has a kind of unstable three-dimensional quality, where I see the image from multiple overlapping, shifting perspectives, kinda like a Cubist painting. Different parts of the image have more or less detail over time; I can't hold fine detail about the whole thing simultaneously. If I wanted to draw it, I'd have to pin it to one perspective for long enough, and I can't make my mind do that.

This shouldn't be so surprising -- perspective and realistic representational art took a long time to develop in human history. It's a skill that has to be learned, and I haven't learned it.

Some people really can imagine a photorealistic picture of the bike though. They're usually either savants or trained artists.