This is mere propaganda. The majority accepted a 4th century date.
Apart from the Eusebian apparatus, which some including Tischendorf have speculated were added at a later date, there are s
ome who opted for a date prior to the 4th century. I can't find any information to support Sir Frederic Madden's (1801–1873) view of a 6th century date, and it seems to have applied only to the Codex Fredrico Augustanus.
HERMAE PASTOR. GRAECĊE, PRIMUM EDIDERUNT ET INTERPRETATIONEM VETEREM LATINAM EX CODICIBUS EMENDATAM ADDIDERUNT RUDOLPHUS ANGER ET GUILIELMUS DINDORF, PROFESSORES LIPSIENSES. 1856 In the above (Latin doc.) You do realize, I hope, that this Greek edition has "great tribulation", and not "say to...
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Uspensky, Hilgenfeld, Madden (if the CFA is later, then Sinaiticus is later) and Donaldson were among those who rejected the 4th century date in the 1860s. Benjamin Harris Cowper showed some of the problems with the early date.
It is best to examine the arguments rather than make silly propaganda pronouncements. Tischendorf became maniacal about his dating theory, as is seen in the titles of his 1863 books. Generally he did a poor job in actually addressing the arguments.
Of course generally the manuscript was hidden from the scholars, and Tischendorf especially did not want them to see both the CFA and the bulk in St. Petersburg. That would raise obvious problems.
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Also interesting is the fact that his attack on Hermas is still in the 1863 Hermas edition.
Allard Pierson (1831-1896) also has a good Hermas section, including Maximus.