I have the same problem with my new MacBook. I had another problem with sms texts not showing up so I made a genius appt. I told the "genius" about the instant hotspot and he told me it was working fine, that they showed up as instant hotspots under Mavericks and not Yosemite and you had to have personal hotspot turned on. I argued with him and he proceeded to tell me he's been an apple tech for 7 years blah blah. Arrogant SOB. I tried to find some online documentation to prove him wrong but I could only find a 9to5Mac article and he discounted its since "it's not an Apple site".
Bill