I would say it's neither a myth nor a fact....Like most said, it Depends from person to person and varies from cirumstance to circumstance....
IMO there is a faint line between a girl and a boy being 'just' friends and 'best' friends....Being 'just' friends is sharing everything with them and having fun, ofcourse! But 'best' friend simply means he/she is the ONLY friend above all your friends....This does indicate that person is 'special' for you...Now it again depends in what way is he/she special and how much is he/she special! But the thing that the person is special itself indicates you have some sort of feelings for him/her, I'm not saying they HAVE to be those feelings of 'love', but there are those special feelings definately! The intensity of those feelings decides whether he/she is 'in love' with that person or simply 'loves' that person, just like Anu said to Taani that he loves her but he isn't in love with her....!! This means Anu has special feelings for Taani, but he hasn't realised the extent and intensity of those feelings! Hopefully, I made sense...:P Btw, if we think acc to what is shown in reel life, it's basically shown like this that best friends fall in love bcoz eventually those two 'best' friends are destined to be the leads of the movie/serial by the creatives!😆 It's quite different and variant in real life...😊