If I possess, e.g., a certain quantity of U235, the government can act on the material, e.g., confiscate it because it is a physical entity. Meanwhile, I can arrive at the knowledge required for encryption, and even an encrypted message, a priori.
In other words, it is not even slightly comparable.
(1) Anyone who disseminates or makes publicly available content (§ 11 (3)) that is suitable for serving as instruction for an unlawful act referred to in § 126 (1) and is intended to promote or arouse the willingness of others to commit such an act shall be punished with imprisonment of up to three years or a fine.
(2) The same penalty shall apply to anyone who
1. disseminates or makes available to the public content (§ 11 (3)) that is suitable for serving as instructions for an unlawful act referred to in § 126 (1), or
2. gives instructions in public or at a meeting for an unlawful act referred to in Section 126 (1)
in order to encourage or incite others to commit such an act.
"§ 126 Disturbance of public order by threatening to commit criminal offenses
(1) Anyone who, in a manner likely to disturb the public peace,
1. commits one of the cases of breach of the peace specified in § 125a sentence 2 nos. 1 to 4,
2. commits a criminal offense against sexual self-determination in the cases specified in § 177 paragraphs 4 to 8 or § 178,
3. murder (§ 211), manslaughter (§ 212) or genocide (§ 6 of the International Criminal Code) or a crime against humanity (§ 7 of the International Criminal Code) or a war crime (§§ 8, 9, 10, 11 or 12 of the International Criminal Code),
5. a criminal offense against personal freedom in the cases of Section 232 (3) sentence 2, Section 232a (3), (4) or (5), Section 232b (3) or (4), Section 233a (3) or (4), in each case insofar as these are crimes, Sections 234 to 234b, § 239a or § 239b,
6. robbery or extortion (§§ 249 to 251 or § 255),
7. a crime dangerous to the public in the cases of Sections 306 to 306c or 307 (1) to (3), Section 308 (1) to (3), Section 309 (1) to (4), Sections 313, 314 or 315 (3), § 315b (3), § 316a (1) or (3), § 316c (1) or (3) or § 318 (3) or (4), or
8. a dangerous offense in the cases of § 309 (6), § 311 (1), § 316b (1), § 317 (1) or § 318 (1)
shall be punished with imprisonment of up to three years or a fine.
(2) Anyone who, in a manner likely to disturb public peace, knowingly falsely claims that one of the unlawful acts referred to in paragraph 1 is about to be committed shall also be punished.
In other words, it is not even slightly comparable.