Address code review feedback

- Fix comment about available time computation to reflect actual implementation
- Use current time for reconstructed column timestamps instead of max partial timestamp

Co-authored-by: michaelsproul <4452260+michaelsproul@users.noreply.github.com>

beacon_node/beacon_chain/src/block_times_cache.rs

@@ -43,7 +43,7 @@ pub struct BlockDelays {
     pub execution_time: Option<Duration>,
     /// The delay from the start of the slot before the block became available
     ///
-    /// Equal to max(`observed + execution_time`, `all_blobs_observed` or `all_data_columns_observed`).
+    /// Equal to max(`executed`, `all_blobs_observed` or `all_data_columns_observed`) minus slot start time.
     pub available: Option<Duration>,
     /// Time after `available`.
     pub attestable: Option<Duration>,

beacon_node/beacon_chain/src/data_column_verification.rs

@@ -16,7 +16,7 @@ use ssz_types::VariableList;
 use std::iter;
 use std::marker::PhantomData;
 use std::sync::Arc;
-use std::time::Duration;
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
 use tracing::{debug, instrument};
 use types::data::ColumnIndex;
 use types::{
@@ -475,12 +475,10 @@ impl<E: EthSpec> KzgVerifiedCustodyDataColumn<E> {
             spec,
         )?;
 
-        // Use the maximum timestamp from the partial set for reconstructed columns
-        let seen_timestamp = partial_set_of_columns
-            .iter()
-            .map(|col| col.seen_timestamp)
-            .max()
-            .unwrap_or_default();
+        // Use the current time as the seen_timestamp for reconstructed columns
+        let seen_timestamp = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap_or_else(|_| Duration::from_secs(0));
 
         Ok(all_data_columns
             .into_iter()