Filler isn't unusual in a knot. If it's in the back or way out of the playing area it shouldn't matter too much
If I'd paid £240 for a bat I wouldn't expect filler to be even in the same vicinity (let alone being hidden underneath the stickers...) - quite surprised that this appears to be fine with most?
MSR sell bats that look like this for between £30 and £60 on eBay...
Nobody would bat an eyelid as it would be deemed as "the norm" for "cheap imports"