Quote in the Strike Cruiser entry:
a number of strike cruiser designs date far back to the centuries immediately following the development of the Codex Astartes.
Thus Strike Cruisers are designed after the heresy, in a way the codex described. In the following millennia variants are known but rare and limited to older chapter/chapters with many resources.
Now, this means, that any book which says Strike Cruisers operate during or before the heresy are wrong and mistaken.
Um, Horizon, I would humbly suggest that this has been retconned. Since... while I can picture a single author getting it wrong, I have a hard time picturing all of them doing so, since they turn up again and again in the HH series. And various CSM books that take place afterward.
This leads to the question: either the SM have lost a disturbing number of ships sized by CSMs since the Heresy, OR, that they had them to begin with.
I hate to say it, but BFG's rulebooks fluff has been getting retconned off and on, either by GW or FFG since 2003. If you say 'well, it doesn't count as it's new' then you have to take the un-updated IA2, which was written at roughly the same time, and states that SM's have lances. Or you could take the stance that 'new books trump old books', and thus space marines have lances and SC's were around before the heresy, which, by the way, fits better with the whole '40k is a technological downslope' as SC are supposedly hyper advanced and require few crew.
Or you could go back to old issues of WD, and discover that SM ships with lances predate BFG. However, they're built by squats. So...
Like the Leman Russ Vanquisher, they're in, they out, they're in, they're out, they're in...
Strike Cruiser Lances, the Pamela Anderson's Implants of 40k...