This is a known side effect of the extended “temporary” current committee configuration.
WHY ARE THERE FIXED VALIDATORS?
There are 32 validators per each of the 8 shards in each epoch’s committee. 22 of those validators in each of the 8 shards are maintained by the core dev team. 22 is 2/3 of the current size of a shard’s committee. 2/3 of each shard’s committee are required to achieve consensus on the validity of each block mined by the shard. This insures that each shard can achieve consensus, even if all 10 of the community validators in each shard completely fail to participate in committee consensus.
The original roadmap intended this to a be a temporary situation. The “fixed validators” were to be released within 3 months of the mainnet genesis. This would give the network enough time to assure the stability of the community validators was fully demonstrated. During this period the mechanism for penalizing and removing non-participating validators – slashing – was not implemented. The non-participation of community validators was not detrimental to the network: the number of fixed validators insured that consensus would always be achieved during this short transition period.
Work began on scaling the shard committee sizes and it became apparent that the fixed validators could not be released until dynamic committee size was implemented. Slashing also could not be released until this mechanism was fully developed. As the development timeline for dynamic sharding shifted, the timeline for releasing the fixed validators was pushed out a few more months to 6 months of mainnet genesis, then a full year to April 2021, then to Q2 2021 and currently is planned for early Q3 2021.
This leaves the network in what was intended to be a temporary situation – non-participating validators are not slashed from the network and thus earn block rewards for committee participation.
BUT WHY ARE BLOCK REWARDS DISTRIBUTED TO THE NON-PARTICIPATING VALIDATORS?
Because there is no active slashing mechanism, a non-participating validator is seen as “participating” in committee when selected, despite producing no blocks. “Participating” here is effectively the same as “not slashed.” The block rewards are then distributed to all 32 validators in each shard’s committee because all 32 validators fall into the “participating”/“not slashed” definition and thus are eligible to receive an equal portion of a committee’s block rewards.
OK. SO WHY ARE PHYSICALLY OFFLINE VALIDATORS SELECTED TO COMMITTEE?
The eligibility for committee selection is “not slashed” and a properly staked 1750 PRV. Once a validator has properly staked 1750 PRV, the validator is known to the network by the BLS mining key stored on-chain in the pool of validators. There is no IP check, heartbeat or other mechanism to confirm online status of the validator’s node. The scope for this kind of validator node management will likely fall under/rely on the slashing mechanism. However as there is no active slashing, the mining key is never removed from the known pool of properly staked validators and will remain eligible for committee selection until unstaked (or slashing is activated).