Not true. A team can ride a rider but doesn't get in enough meetings for an average(which is now 8 meetings). He is a protected asset then and other teams cannot claim him. The original team must then include him in the next years 1 to 7, at the start of the next season, otherwise he becomes a free agent again and can ride for anyone.
Peter Larsen IIRC, rode only 11 meetings in his first year at Glasgow and was stuck on a 7 point average, having broken his leg I believe. At the next AGM, the BSPA reduced his average to I think 5 to Glasgow, and 4 to anyone else, to help him get a teamplace as his form before the break was in the order of about 4.