I've used those spiles (among others) for four years now. I have always used a standard wood bit, never used a proper tapping bit. Could the tapping bit you have be a tiny bit bigger than my 5/16" bit?
These spiles do seem a bit less tight than some of the other taps and spiles, but I've never had one pull out, even in pretty heavy wind. I guess angle could be part of it. Or if the hole is not even, and is reamed out a bit. Or you got a bad batch of spiles, and they're a bit too small?
2016: Homemade arch from old wood stove; 2 steam tray pans; 6 taps; 1.1 gal
2017: Same setup. 15 taps; 4.5 gal
2018: Same setup. Limited time. 12 taps and short season; 2.2 gal
2019: Very limited time. 7 taps and a short season; 1.8 gals
2020: New Mason 2x3 XL halfway through season; 9 taps 2 gals
2021: Same 2x3, 18 taps, 4.5 gals
2022: 23 taps, 5.9 gals
2023: 23 taps. Added AUF, 13.2 gals
2024: 17 taps, 5.3 gals
All on buckets