This is correct. An antenna preamplifier amplifies anything that the antenna receives. They are mainly intended to overcome signal loss in cabling due to splits to multiple TVs and not to improve reception quality. Only antenna placement will improve reception quality.
To over exaggerate this, imagine if the antenna was inside a lead box. It would not receive any signals. You could still put an amplifier on the line, but the antenna still gets no signal. The amplifier will allow you to split the feed to multiple TVs, but will not remove the obstruction to receiving the signal to begin with (the lead box).
You should take care to place the antenna where it will receive the best quality signal regardless of any amplifiers. An amplifier "can" improve the signal if the antenna is receiving a weak signal. For example, on the fringe of the broadcast area, but the amplifier cannot create a signal if the antenna isn't receiving it.
My view is that indoor antennas are only good if you're within about 15 miles of the broadcast towers. Indoor antennas receive less signal due to lower height and wall obstructions and thus need to have a strong signal to begin with. If you're over 15 miles away, the broadcast signal may no longer be strong enough to overcome losses from walls and such. At that point, you should consider placing the antenna outside.
Of course, radio waves act screwy sometimes and you may find that indoor antennas work well for some people who are much farther away, while some people even closer can't get anything without an outdoor antenna. The more obstructions between you and the broadcast tower (tall trees, other buildings, hills, mountains, rain clouds), the more likely you are to need an outdoor antenna.