Let's be clear on what a footprint is first...I would define a footprint as a common characteristic that is shared between two or more PBN sites. In order for a footprint to exist it has to be detectable, most outward facing Wordpress Plugins impact the HTML of a webpage whereas Spyder Spanker does not (just right click your site and go to 'view source' to see this).
You could argue that blocking bots is a footprint, however your .htaccess file its self which is responsible for this, is invisible to the public and instead functions simply as a set of rules for your web-server to follow when it's deciding to accept or deny get, head or post requests. Google can't detect blocked bots, even if it was impersonating that bot (extremely unlikely) it would simply receive a host not found response from your web-server.
tl;dr Spyder Spanker and bot blocking is not a footprint. Personally, I choose to always block bots but only via the .htaccess file which seems to do the trick...the following code should be fine:
SetEnvIfNoCase User-Agent .*rogerbot.* bad_bot
SetEnvIfNoCase User-Agent .*exabot.* bad_bot
SetEnvIfNoCase User-Agent .*mj12bot.* bad_bot
SetEnvIfNoCase User-Agent .*dotbot.* bad_bot
SetEnvIfNoCase User-Agent .*gigabot.* bad_bot
SetEnvIfNoCase User-Agent .*ahrefsbot.* bad_bot
SetEnvIfNoCase User-Agent .*sitebot.* bad_bot
<Limit GET POST HEAD>
Order Allow,Deny
Allow from all
Deny from env=bad_bot
</Limit>