Spam received but not from contact form?

Hello and thanks for your great plugins. I have noticed that when using Flamingo and clearing out the spam email there is a Channels filter where supposedly i can see which form was used to deliver the spam. I have two contact forms in the filter dropdown. Selecting either brings up only one email out of 200 spam emails. Is this a filter that only works on the valid emails or does it work for the spam also. I ask this question because it seems that if spam is not using either form, them spam is bypassing the contact forms but Flamingo inbound messages still captures them. Are spammers able to do this? If so can I close that door and force all inbound mail to only come through these forms? I searched but could not find this topic in forums or Googling.