Maybe yes, maybe no. I say it depends on the subject, the designer and the builder.

For example:

http://www.allaboutguppys.com/supgup/gupcomp.mov

This is a video of the Super Guppy model I designed and that my brother and I built and video of the full-size prototype merged for a side-by-side comparison (so to speak) of the scale speed of the model.

Scale speed CAN BE DONE.

It just takes a model with a light enough wing loading so that it doesn't stall while flying at the scale speed.

Dan