If not doing conjugate match can things go wrong if effect of feed transmission line impedance is taken in account, if transmission line have a decent length relative wavelength.
To make thing simpler, assume no reactance in below example:
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It is a bit worst case with for example a 20 mm long PCB transmission line at 2.4GHz, but 50% loss can be bad enough for its power economy and battery weight if it is a battery powered wearable of some kind compeating with concurrent to have smallest IoT thing and longest working time and best RF coverage for a single battery charge, such as a inear headset.
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