Thank you Joshua, I was thinking about edit_features, I'll give it a go.
Taking advantage of opportunity (please let me know if you'd prefer me to open new question) - I try to run something like this:
<SPAN class="comment token"># below returns response suggesting query is correct</SPAN>
table<SPAN class="punctuation token">.</SPAN>validate_sql<SPAN class="punctuation token">(</SPAN>sql<SPAN class="operator token">=</SPAN><SPAN class="string token">"my_timestamp_column < TIMESTAMP '2019-01-06 11:00:00'"</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="comment token"># below throws exception</SPAN>
table<SPAN class="punctuation token">.</SPAN>delete_features<SPAN class="punctuation token">(</SPAN>where<SPAN class="operator token">=</SPAN><SPAN class="string token">"my_timestamp_column < TIMESTAMP '2019-01-06 11:00:00'"</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="line-numbers-rows"><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN></SPAN>
Line 5 fails with exception:
Traceback <SPAN class="punctuation token">(</SPAN>most recent call last<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
File <SPAN class="string token">"harvester/test/simulate_entry_point.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">40</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> <SPAN class="operator token"><</SPAN>module<SPAN class="operator token">></SPAN>
route_event<SPAN class="punctuation token">(</SPAN>
File <SPAN class="string token">"/lib/python3.8/site-packages/arcgis/features/layer.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">1446</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> delete_features
<SPAN class="keyword token">return</SPAN> self<SPAN class="punctuation token">.</SPAN>_con<SPAN class="punctuation token">.</SPAN>post<SPAN class="punctuation token">(</SPAN>path<SPAN class="operator token">=</SPAN>delete_url<SPAN class="punctuation token">,</SPAN> postdata<SPAN class="operator token">=</SPAN>params<SPAN class="punctuation token">,</SPAN> token<SPAN class="operator token">=</SPAN>self<SPAN class="punctuation token">.</SPAN>_token<SPAN class="punctuation token">)</SPAN>
File <SPAN class="string token">"/lib/python3.8/site-packages/arcgis/_impl/connection.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">1183</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> post
self<SPAN class="punctuation token">.</SPAN>_handle_json_error<SPAN class="punctuation token">(</SPAN>resp_json<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'error'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN> errorcode<SPAN class="punctuation token">)</SPAN>
File <SPAN class="string token">"/lib/python3.8/site-packages/arcgis/_impl/connection.py"</SPAN><SPAN class="punctuation token">,</SPAN> line <SPAN class="number token">1204</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="keyword token">in</SPAN> _handle_json_error
<SPAN class="keyword token">raise</SPAN> RuntimeError<SPAN class="punctuation token">(</SPAN>errormessage<SPAN class="punctuation token">)</SPAN>
RuntimeError<SPAN class="punctuation token">:</SPAN>
Unable to delete features<SPAN class="punctuation token">.</SPAN>
<SPAN class="punctuation token">(</SPAN>Error Code<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">400</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="line-numbers-rows"><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN></SPAN>
There is only 40 items meeting criteria so should not be hitting any limits.
I think this might be due to open-ended nature of the query (although I'd like arcgis to delete all features meeting criteria, I have seen posts here where people had to run multiple queries with bundles of ~2000 items).