Just to simplify things, if you have two antennas of a particular type - in this case chip antennas mounted on circuit boards - and these antennas are physically oriented the same way (i.e. their tops point "up" and each of their other corresponding faces are similarly oriented) then their polarizations are matched. For antennas on mobile devices, polarization is useful as a measurement reference, but since the devices orientation is uncontrolled then it is useful (to me, at least) to consider best & worst cases. This is one reason for looking at the radiation patterns for different antenna geometries - to see if they have any potentially troublesome "dark sides."
Your use case sounds something like a biometric telemetry application in which one or more devices attach to the body and collect data describing things like temperature and heart rate and then transmit this data to one or more other devices (likely also in close proximity to the same body). In such a case you may have some control over the sensor antenna orientation, but the receiving device may be in any orientation. If you don't have an omnidirectional radiation pattern then you may discover that, under some conditions, you don't have a reliable signal at either or both sides of the "conversation."
This may not be a problem with Class II devices, which can transmit signals well beyond the range of a physical Personal Area Network (10 meters is beyond my own reach). With such a transmit power level you may not have any real problems, even when antennas are not optimally oriented.
Another factor in your favor is that people tend to be around things that reflect RF signals. Even if you have a master and a slave located on opposite sides of a very large person who, for some reason, absorbs abnormally high amounts of 2.4GHz signals, nearby objects may reflect enough energy to allow the system to work fine anyway.
Ultimately, you can do some empirical testing out in a field (or in a wooden boat on a lake...or something) and see what happens when you move the radios around with respect to each other. I suspect that you are okay if you are using an off-the-shelf Bluetooth module.
Lastly, if you are developing a proprietary system (and not creating "dongles" that communicate with a 3rd party device, such as a smart phone), then you might consider using a Body Area Network rather than a radiated energy system. I don't know what your application is or what bandwidth you might need, but body area networks can be a very reliable and low energy means of shipping data among points on the human body.
Best wishes.