[Amps] HyGain HyTower Question

[Bob Maser]

This is COMPLETELY off the subject for this amplifier group but you guys 
always amaze me as to how much intelligence is dialed in so forgive my 
question.  I am building a heavy duty version of the HyGain Hytower vertical 
and I plan on using it on 160,75,40 and 20 meters.  It will be capable of 
handling my 3X3 amp(see, it is an amp related topic).  My dilemma is that 
Hygain says that the combined length of the aluminum stinger and the wire 
coming down inside the tower will act as a 3/4 wavelength radiator on 20M 
AND the same stinger plus the wire will be a 1/4 wavelength on 75.  How can 
this be?  234*3/14.2 = 49.4 feet 3/4 wavelength on 14.2. and 234*1/3.8 = 
61.6 feet 1/4 wavelength on 3.8.  They aren't even close to each other. 
They specifically say that the stinger and the wire coming down thru the 
tower are used on both bands and there are no stub decouplers used for 
either 20 or 75.  On the other bands they do use decoupling stubs to get it 
to resonate as a 1/4 wavelength.

What am I missing here?

Bob W6TR