no. luck. here the math:
Bn,p(x)
n = ammount of games played
p = position chance (.5 on 2 player maps and .25 on 4 player maps)
x = same position for x games out of n
some examples:
you played 10 games on TS, the chance that you play on one position for 5 times is:
B10;0.5(5) = 0.246 equals: 25%
for 8 out of 10 being on same position:
B10;0.5(8) = 0.0439 equals: 4%
for 10 out of 10: its 9.7E-4 ... means 0.00097 equals: 0.097%
So you basicly got very lucky.