For WT_SESSION::verify (or other operations that need exclusive access to a file such as WT_SESSION::salvage), a change was made in WT-4070 to disallow closing trees if they are dirty and a stable timestamp is set:

	/*
	 * Don't flush data from trees when there is a stable timestamp set:
	 * that can lead to files that are inconsistent on disk after a crash.
	 */
	if (btree->modified && !bulk &&
	    S2C(session)->txn_global.has_stable_timestamp &&
	    !__wt_btree_immediately_durable(session))
		return (__wt_set_return(session, EBUSY));

daniel.gottlieb raises the point is that this change is only effective when a stable timestamp has been set. When there will be no stable timestamp and if logging is disabled, crashing during/soon after a verify could leave data inconsistent on disk.

Given that, the test above should be extended to also return EBUSY for modified, non-bulk trees when global logging is disabled.