Why this site´s SE redirect has not been detected?

No Sucuri SiteCheck does not flag, nor does Quttera’s for that matter. Only killmalware has it.
Re: http://killmalware.com/gfxd.de/ (kicking up a 410 gone). We get 2 errors and 4 warnings here: https://mxtoolbox.com/domain/gfxd.de/
Did not expect AOS to flag as it does not flag casino websites as a rule of thumb.
Here we see Vautron Serverhousing abuse: http://toolbar.netcraft.com/site_report?url=www.casino-freispiele.com

A crypto report gives some results: gfxd.de
This is not a Symantec certificate.
Please contact the Certificate Authority for further verification.
You have 1 error
Wrong certificate installed.
The domain name does not match the certificate common name or SAN.
Warnings
BEAST
The BEAST attack is not mitigated on this server.
RC4
This server uses the RC4 cipher algorithm which is not secure. Disable the RC4 cipher suite and update the server software to support the Advanced Encryption Standard (AES) cipher algorithm. Contact your web server vendor for assistance.
SSLv3
This server uses the SSLv3 protocol which is not secure. Disable the SSLv3 protocol and enable a higher protocol version. Contact your web server vendor for assistance.
Root installed on the server.
For best practices, remove the self-signed root from the server.
This server is vulnerable to:
Poodle (SSLv3)
This server is vulnerable to a Poodle (SSLv3) attack. If you have not disabled SSLv3 fallback support, disable it now and use TLS 1.2 or higher.
Certificate information
Common name:
ax.falkmeier.com
SAN:

Valid from:
2015-Aug-13 12:40:35 GMT
Valid to:
2016-Aug-12 12:40:35 GMT
Certificate status:
Unknown
Revocation check method:
Not available
Organization:
Parallels, GmbH.
Organizational unit:
Parallels Confixx
City/locality:
Herndon
State/province:
Virginia
Country:
US
Certificate Transparency:
Not Enabled
Serial number:
00aab0e1df099a114c
Algorithm type:
SHA1withRSA
Key size:
2048
Certificate chainShow details
ax.falkmeier.comRoot certificate

So BEAST and POODLE vulnerable.

Bad R-Status here: https://securityheaders.io/?q=http%3A%2F%2Fgfxd.de
following the redirect we get a F-Status: https://securityheaders.io/?q=http%3A%2F%2Fwww.casino-freispiele.com%2F10-1%2F4460%2FVirtual-City.html

Excessive server header info proliferation and vulnerable PHP version: http://fetch.scritch.org/%2Bfetch/?url=http%3A%2F%2Fwww.casino-freispiele.com&useragent=Fetch+useragent&accept_encoding=

18 other domains on that server: https://whois.domaintools.com/gfxd.de
On their servers runs ProFTPD or KnFTPD & OpenSSH 6.0p1 Debian 4+deb7u2 (protocol 2.0)
via ax.falkmeier.com, pipelining. Site doesn’t have a title (text/html).
As we have seen from the Crypto report this cert runs: ssl-cert: Subject: commonName=ax.falkmeier.com/organizationName=Parallels, GmbH./stateOrProvinceName=Virginia/countryName=US bad zone - falkmeier dot com → http://www.dnsinspect.com/falkmeier.com/1461839927 (seems OK).
But we land here: http://www.falkmeier.de/8-0/impressum.html
http://toolbar.netcraft.com/site_report?url=http://www.falkmeier.de (not very transparent set-up to say the least).
See where Google ‘gets blind on one eye as long as clicks will pay’ ;D (iron.).

polonus (volunteer website security analyst and website error-hunter)