The reference points are provided by my upthread "Coin Days Destroyed"["coin age"] suggestion a few days ago and the point yesterday in this thread about hard-coding the destination addresses in the CLTV. In order words, those reference points do not depend on future confirmations, but are past history (the age of the UXTOs being spent) and future invariants (the hard-coded destinations).
Although the "coin age" reference points are not absolute, i.e. could be rewritten by a chain reorganization attack, this will not reduce the squelching effect on a jamming attack, because that hashrate attack costs electricity (in PoW) and with the dual CLTV DE protocol, the attacker is not reimbursed.
The hard-coded destinations of a dual CLTV DE protocol obviously can't be altered by any hashrate attack so thus are absolute reference points.