It appears that the Phillipines may have their own interpretation on this.
http://www.caap.gov.ph/Downloads/AO91.pdf contains the information (p.14) that Flashing White to an aircraft in flight means "Land at this aerodrome and proceed to the apron". However, that is information for the pilot rather than a clearance to do so, because there's a note which says that "Clearance to land and to taxi will be given in due course"
So it seems that the tower controller could legitimately use flashing white in this situation, but would have had to follow it with a Steady Green then a Flashing Green to give you the actual landing and taxi clearances.
FWIW, in this part of the world (Oz), flashing white to an aircraft in flight has no significance (
http://www.airservicesaustralia.com/.../1_5_40-48.pdf) and I would have had a similar reaction to you