Yes, not all women get these patterns. Some do and some don't. I have had triphasic patterns when I was not pregnant so it is def not def if you do see one.
If you're pregnant, you'll notice a biphasic or triphasic pattern fairly early in the chart. Not all women will see a clear triphasic pattern. The key is that BBTs stays above the coverline during the luteal phase, so that your body produces a sufficient lining for the fertilized egg in which to plant. However, there may be a dip part way through when the body produces a slight surge in estrogen. Though this dip isn't common when the egg has been fertilized.
I had a tri phasic but on fertility friend the ones who did not stayed up and some had a dip one day but they where all up like after O.
For me I had a drop in temps day before ovulation,to signal me it was happening,triphastic would show up regardless thats if you were using a online chart.temps will spike now and then both before and after o,as long as they stay above coverline after ovulation your ok,some say there is an implantation dip shown on a chart,but this isnt necessary true,fertility friend,allows you to check out peoples success charts etc.