Is anything bad on exclusion crawl rules in SharePoint 2013?

Using SP2013, we have disputation on using crawl rules to handle application specific requirements within an on-prem farm.

I'm providing an application (site collection with features) that contains several lists with attachments containing various files (Office, zip, pdf,..). There is also some logic and custom forms but it's not relevant for this question. The business rule for this application is that all searches work only on direct list content but never on its attachments (i.e. the owner of the app does not want the attachments to be searchable). There are several gigabytes of data in attachments. So I defined exclusion crawl rule for list attachments (like *://host-name-site-col-url/.*/attachments/.*) to be set in Search Administration.

Now, I was asked by farm admin to create Custom Query instead of crawl rule because crawl rules affect the whole farm. Sure, it is farm-level setting but if I create Custom Query, I may refine the results but I will not exclude the attachments from being crawled.

Any opinion on this? Is defining crawl rules for application requirements bad idea?