I just tested my 9' whip (mounted on the roo-guard of my Dodge). Tied
it back so the top was parallel with the ground (pointing East, if
that makes a difference). Measurements were compared to the antenna
straight up.......;

SWR didn't change at all, and vertically polarized field strength
dropped by a hair. However, horizontally polarized field strength made
a huge jump to the good. Subjectively, I listened to the toilet bowl
while pulling on the lanyard. Some weak signals disappeared while
others came in that weren't there before. Let the whip go back to
vertical and the old signals came back while the new signals were
lost.

Let's see..............An antennas bent so that the tip is parallel to
the ground?.............That represents an antenna that is now midway
between horizontal and vertical polarization.

The theoretical gain of that antenna should be equal between
polarizations. When such a scenario is in place the field strength
should drop to .707 of it's original. That represents a 3db loss
just from this antenna being bent.

Yet you stated....................................

"vertically polarized field strength dropped by a hair."

When testing mobile antennas a 3db loss is huge.
Most all well designed efficient non bent antennas
will easily beat your -3db antenna.