Allowed spread check allows for smaller spread than expected, because spread percentage is calculated from value after swaps, not before. 
So, the check is actually if value ETH after * _allowedSpread >= deposit ETH value. However, the calculation checks if the spread is actually lower than set by user, because the slippage is applied to already diminished value. For example, lets say that user passes the following:
So slippage down to 95 should be accepted. However, due to the flipped calculations, the slippage check would look like 95 * 105% < 100 => 99.75 < 100 and would revert, even though it should be accepted.
