Very possible. STI fluctuation is +/- 15% (against capital). I have been invested in the ETF for more than six years via RSP and when I look at my closing balance each year I can see the trend.
Against my capital investment at the end of each year:
2014: +4.5%
2015: -9.2% (>15% Loss)
2016: -5.6% (> 4% Grain)
2017: 11% (> 15% Grain)
2018: -1% (> 12% Loss)
2019: 2.8% (> 3% Gain)
2020 (to date): -20% (> 22% Loss)
I did not considered dividend received, just capital gain/loss. It is true that the point of entry and exit can greatly impact the returns. It can be argued because my calculation is based on RSP and lump sum investment may be different. I dunno. But from my personal stats I can see the fluctuation. I am not sure why you said the STI had minimal growth. If we look at just growth alone then it is true that STI did not grow much. However the fluctuation in between can kill us or help us make some good returns.
These stats don't seem correct. As far as I know, STI has had minimal growth in the last 10 years.